From Princeton: “Researchers find path to discovering new topological materials, holding promise for technological applications”

Princeton University

July 20, 2017
No writer credit

Researchers have discovered how to identify new examples of topological materials, which have unique and desirable electronic properties. The technique involves finding the connection between band theory, which describes the energy levels of electrons in a solid, with a material’s topological nature. The disconnected bands indicate the material is a topological insulator. Image courtesy of Nature.

Researchers find path to discovering new topological materials, holding promise for technological applications.

An international team of researchers has found a way to determine whether a crystal is a topological insulator — and to predict crystal structures and chemical compositions in which new ones can arise. The results, published July 20 in the journal Nature, show that topological insulators are much more common in nature than currently believed.

Topological materials, which hold promise for a wide range of technological applications due to their exotic electronic properties, have attracted a great deal of theoretical and experimental interest over the past decade, culminating in the 2016 Nobel Prize in physics. The materials’ electronic properties include the ability of current to flow without resistance and to respond in unconventional ways to electric and magnetic fields.

Until now, however, the discovery of new topological materials occurred mainly by trial and error. The new approach described this week [see above reference to the Nature article] allows researchers to identify a large series of potential new topological insulators. The research represents a fundamental advance in the physics of topological materials and changes the way topological properties are understood.

The team included: at Princeton University, Barry Bradlyn and Jennifer Cano, both associate research scholars at the Princeton Center for Theoretical Science, Zhijun Wang, a postdoctoral research associate, and B. Andrei Bernevig, professor of physics; professors Luis Elcoro and Mois Aroyo at the University of the Basque Country in Bilbao; assistant professor Maia Garcia Vergniory of University of the Basque Country and Donostia International Physics Center (DIPC) in Spain; and Claudia Felser, professor at the Max Planck Institute for Chemical Physics of Solids in Germany.

“Our approach allows for a much easier way to find topological materials, avoiding the need for detailed calculations,” Felser said. “For some special lattices, we can say that, regardless of whether a material is an insulator or a metal, something topological will be going on,” Bradlyn added.

Until now, of the roughly 200,000 materials catalogued in materials databases, only around a few hundred are known to host topological behavior, according to the researchers. “This raised the question for the team: Are topological materials really that scarce, or does this merely reflect an incomplete understanding of solids?” Cano said.

To find out, the researchers turned to the nearly century-old band theory of solids, considered one of the early landmark achievements of quantum mechanics. Pioneered by Swiss-born physicist Felix Bloch and others, the theory describes the electrons in crystals as residing in specific energy levels known as bands. If all the states in a group of bands are filled with electrons, then the electrons cannot move and the material is an insulator. If some of the states are unoccupied, then electrons can move from atom to atom and the material is capable of conducting an electrical current.

Because of the symmetry properties of crystals, however, the quantum states of electrons in solids have special properties. These states can be described as a set of interconnected bands characterized by their momentum, energy and shape. The connections between these bands, which on a graph resemble tangled spaghetti strands, give rise to topological behaviors such as those of electrons that can travel on surfaces or edges without resistance.

The team used a systematic search to identify many previously undiscovered families of candidate topological materials. The approach combined tools from such disparate fields as chemistry, mathematics, physics and materials science.

First, the team characterized all the possible electronic band structures arising from electronic orbitals at all the possible atomic positions for all possible crystal patterns, or symmetry groups, that exist in nature, with the exception of magnetic crystals. To search for topological bands, the team first found a way to enumerate all allowed non-topological bands, with the understanding that anything left out of the list must be topological. Using tools from group theory, the team organized into classes all the possible non-topological band structures that can arise in nature.

Next, by employing a branch of mathematics known as graph theory — the same approach used by search engines to determine links between websites — the team determined the allowed connectivity patterns for all of the band structures. The bands can either separate or connect together. The mathematical tools determine all the possible band structures in nature — both topological and non-topological. But having already enumerated the non-topological ones, the team was able to show which band structures are topological.

By looking at the symmetry and connectivity properties of different crystals, the team identified several crystal structures that, by virtue of their band connectivity, must host topological bands. The team has made all of the data about non-topological bands and band connectivity available to the public through the Bilbao Crystallographic Server. “Using these tools, along with our results, researchers from around the world can quickly determine if a material of interest can potentially be topological,” Elcoro said.

The research shows that symmetry, topology, chemistry and physics all have a fundamental role to play in our understanding of materials, Bernevig said. “The new theory embeds two previously missing ingredients, band topology and orbital hybridization, into Bloch’s theory and provides a prescriptive path for the discovery and characterization of metals and insulators with topological properties.”

David Vanderbilt, a professor of physics and astronomy at Rutgers University who was not involved in the study, called the work remarkable. “Most of us thought it would be many years before the topological possibilities could be catalogued exhaustively in this enormous space of crystal classes,” Vanderbilt said. “This is why the work of Bradlyn and co-workers comes as such a surprise. They have developed a remarkable set of principles and algorithms that allow them to construct this catalogue at a single stroke. Moreover, they have combined their theoretical approach with materials database search methods to make concrete predictions of a wealth of new topological insulator materials.”

The theoretical underpinnings for these materials, called “topological” because they are described by properties that remain intact when an object is stretched, twisted or deformed, led to the awarding of the Nobel Prize in physics in 2016 to F. Duncan M. Haldane, Princeton’s Sherman Fairchild University Professor of Physics; J. Michael Kosterlitz of Brown University; and David J. Thouless of the University of Washington.

Chemistry and physics take different approaches to describing crystalline materials, in which atoms occur in regularly ordered patterns or symmetries. Chemists tend to focus on the atoms and their surrounding clouds of electrons, known as orbitals. Physicists tend to focus on the electrons themselves, which can carry electric current when they hop from atom to atom and are described by their momentum.

“This simple fact — that the physics of electrons is usually described in terms of momentum, while the chemistry of electrons is usually described in terms of electronic orbitals — has left material discovery in this field at the mercy of chance,” Wang said.

“We initially set out to better understand the chemistry of topological materials — to understand why some materials have to be topological,” Vergniory said.

Aroyo added, “What came out was, however, much more interesting: a way to marry chemistry, physics and mathematics that adds the last missing ingredient in a century-old theory of electronics, and in the present-day search for topological materials.”

Funding for the study was provided by the U.S. Department of Energy (DE-SC0016239), the U.S. National Science Foundation (EAGER DMR-1643312 and MRSEC DMR-1420541), and the U.S. Office of Naval Research (N00014-14-1-0330). Additional funding came from a Simons Investigator Award, the David & Lucile Packard Foundation, and Princeton University’s Eric and Wendy Schmidt Transformative Technology Fund. Funding was also provided by the Spanish Ministry of Economy and Competitiveness (FIS2016-75862-P and FIS2013-48286-C2-1-P), the Government of the Basque Country (project IT779-13), and the Spanish Ministry of Economy and Competitiveness and European Federation for Regional Development (MAT2015-66441-P).

The study, Topological quantum chemistry, by Barry Bradlyn, Luis Elcoro, Jennifer Cano, Maia Garcia Vergniory, Zhijun Wang, Claudia Felser, Mois Aroyo and B. Andrei Bernevig, was published in the journal Nature on July 20, 2017.

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About Princeton: Overview

Princeton University is a vibrant community of scholarship and learning that stands in the nation’s service and in the service of all nations. Chartered in 1746, Princeton is the fourth-oldest college in the United States. Princeton is an independent, coeducational, nondenominational institution that provides undergraduate and graduate instruction in the humanities, social sciences, natural sciences and engineering.

As a world-renowned research university, Princeton seeks to achieve the highest levels of distinction in the discovery and transmission of knowledge and understanding. At the same time, Princeton is distinctive among research universities in its commitment to undergraduate teaching.

Today, more than 1,100 faculty members instruct approximately 5,200 undergraduate students and 2,600 graduate students. The University’s generous financial aid program ensures that talented students from all economic backgrounds can afford a Princeton education.

From BNL: “Electron Orbitals May Hold Key to Unifying Concept of High-Temperature Superconductivity”

Brookhaven Lab

July 6, 2017
Karen McNulty Walsh,
kmcnulty@bnl.gov
(631) 344-8350

Peter Genzer
genzer@bnl.gov
(631) 344-3174

Iron-based superconductivity occurs in materials such as iron selenide (FeSe) that contain crystal planes made up of a square array of iron (Fe) atoms, depicted here. In these iron layers, each Fe atom has two active electron “clouds,” or orbitals—dxz (red) and dyz (blue)—each containing one electron. By directly visualizing the electron states in the iron planes of FeSe, the researchers revealed that that electrons in the dxz orbitals (red) do not form Cooper pairs or contribute to the superconductivity, but instead form an incoherent metallic state along the horizontal (x) axis. In contrast, all electrons in the dyz orbitals (blue) form strong Cooper pairs with neighboring atoms to generate superconductivity. Searching for other materials with this exotic “orbital-selective” pairing may lead to the discovery of new superconductors. No image credit.

The custom-built Spectroscopic Imaging Scanning Tunneling Microscope used for these experiments stands one meter high, with cryogenic circuitry at the top for cooling samples to temperatures just above absolute zero (nearly -273 degrees Celsius). Inside, a needle with single atom on the end scans across the crystal surface in steps as small as 2 trillionths of a meter, measuring the electron tunneling current at each location. These measurements reveal the quantum wavefunctions of electrons in the material with exquisite precision. No image credit.

A team of scientists has found evidence for a new type of electron pairing that may broaden the search for new high-temperature superconductors. The findings, described in the journal Science, provide the basis for a unifying description of how radically different “parent” materials—insulating copper-based compounds and metallic iron-based compounds—can develop the ability to carry electrical current with no resistance at strikingly high temperatures.

According to the scientists, the materials’ dissimilar electronic characteristics actually hold the key to commonality.

See the full article here .

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One of ten national laboratories overseen and primarily funded by the Office of Science of the U.S. Department of Energy (DOE), Brookhaven National Laboratory conducts research in the physical, biomedical, and environmental sciences, as well as in energy technologies and national security. Brookhaven Lab also builds and operates major scientific facilities available to university, industry and government researchers. The Laboratory’s almost 3,000 scientists, engineers, and support staff are joined each year by more than 5,000 visiting researchers from around the world. Brookhaven is operated and managed for DOE’s Office of Science by Brookhaven Science Associates, a limited-liability company founded by Stony Brook University, the largest academic user of Laboratory facilities, and Battelle, a nonprofit, applied science and technology organization.

From Ames Lab- “Scientists’ surprising discovery: making ferromagnets stronger by adding non-magnetic element”

Ames Laboratory

June 23, 2017
Yaroslav Mudryk
Division of Materials Science and Engineering
(515) 294-2728
slovkomk@ameslab.gov

Durga Paudyal
Division of Materials Science and Engineering
(515)-294-2041
durga@ameslab.gov

Laura Millsaps
Ames Laboratory Public Affairs
(515) 294-3474
millsaps@ameslab.gov

No image caption or credit.

Researchers at the U.S. Department of Energy’s Ames Laboratory discovered that they could functionalize magnetic materials through a thoroughly unlikely method, by adding amounts of the virtually non-magnetic element scandium to a gadolinium-germanium alloy.

It was so unlikely they called it a “counterintuitive experimental finding” in their published work on the research.

“People don’t talk much about scandium when they are talking magnetism, because there has not been much reason to,” said Yaroslav Mudryk, an Associate Scientist at Ames Laboratory. “It’s rare, expensive, and displays virtually no magnetism.”

“Conventional wisdom says if you take compound A and compound B and combine them together, most commonly you get some combination of the properties of each. In the case of the addition of scandium to gadolinium, however, we observed an abrupt anomaly.”

Years of research exploring the properties of magnetocaloric materials, relating back to the discovery of the giant magnetocaloric effect in rare earth alloys in 1997 by Vitalij Pecharsky and the late Karl Gschneidner, Jr., laid the groundwork for computational theory to begin “hunting” for hidden properties in magnetic rare-earth compounds that could be discovered by introducing small amounts of other elements, altering the electronic structure of known materials.

“From computations, we projected that scandium may bring something really unusual to the table: we saw an unexpectedly large magnetic moment developing on its lone 3d electron,” said Ames Laboratory Associate Scientist Durga Paudyal. “It is the hybridization between gadolinium 5d and the scandium 3d states that is the key that strengthens magnetism with the scandium and transforms it to a ferromagnetic state.”

“Basic research takes time to bear fruit. This is an exemplary case when 20 years ago our team started looking into what are called the 5:4 compounds,” said Ames Laboratory group leader and Iowa State University Distinguished Professor Vitalij Pecharsky. “Only now we have learned enough about these unique rare earth element-containing materials to become not only comfortable but precise in predicting how to manipulate their properties at will.”

The discovery could greatly change the way scandium and other ‘conventionally’ non-magnetic elements are considered and used in magnetic materials research and development, and possibly creates new tools for controlling, manipulating, and functionalizing useful magnetic rare-earth compounds.

The research is further discussed in the paper, Enhancing Magnetic Functionality with Scandium: Breaking Stereotypes in the Design of Rare Earth Materials, authored by Yaroslav Mudryk, Durga Paudyal, Jing Liu, and Vitalij K. Pecharsky; and published in the Chemistry of Materials.

The work was supported by the U.S. Department of Department of Energy’s Office of Science.

Ames Laboratory is a U.S. Department of Energy Office of Science national laboratory operated by Iowa State University. Ames Laboratory creates innovative materials, technologies and energy solutions. We use our expertise, unique capabilities and interdisciplinary collaborations to solve global problems.

DOE’s Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit http://science.energy.gov.

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Ames Laboratory is a government-owned, contractor-operated research facility of the U.S. Department of Energy that is run by Iowa State University.

For more than 60 years, the Ames Laboratory has sought solutions to energy-related problems through the exploration of chemical, engineering, materials, mathematical and physical sciences. Established in the 1940s with the successful development of the most efficient process to produce high-quality uranium metal for atomic energy, the Lab now pursues a broad range of scientific priorities.

Ames Laboratory is a U.S. Department of Energy Office of Science national laboratory operated by Iowa State University. Ames Laboratory creates innovative materials, technologies and energy solutions. We use our expertise, unique capabilities and interdisciplinary collaborations to solve global problems.

Ames Laboratory is supported by the Office of Science of the U.S. Department of Energy. The Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov.

From SLAC: “A Single Electron’s Tiny Leap Sets Off ‘Molecular Sunscreen’ Response”

SLAC Lab

June 22, 2017
Glennda Chui

Thymine – the molecule illustrated in the foreground – is one of the four basic building blocks that make up the double helix of DNA. It’s such a strong absorber of ultraviolet light that the UV in sunlight should deactivate it, yet this does not happen. Researchers used an X-ray laser at SLAC National Accelerator Laboratory to observe the infinitesimal leap of a single electron that sets off a protective response in thymine molecules, allowing them to shake off UV damage. (Greg Stewart/SLAC National Accelerator Laboratory)

In experiments at the Department of Energy’s SLAC National Accelerator Laboratory, scientists were able to see the first step of a process that protects a DNA building block called thymine from sun damage: When it’s hit with ultraviolet light, a single electron jumps into a slightly higher orbit around the nucleus of a single oxygen atom.

This infinitesimal leap sets off a response that stretches one of thymine’s chemical bonds and snaps it back into place, creating vibrations that harmlessly dissipate the energy of incoming ultraviolet light so it doesn’t cause mutations.

The technique used to observe this tiny switch-flip at SLAC’s Linac Coherent Light Source (LCLS) X-ray free-electron laser can be applied to almost any organic molecule that responds to light – whether that light is a good thing, as in photosynthesis or human vision, or a bad thing, as in skin cancer, the scientists said. They described the study in Nature Communications today.

SLAC/LCLS

“All of these light-sensitive organic molecules tend to absorb light in the ultraviolet. That’s not only why you get sunburn, but it’s also why your plastic eyeglass lenses offer some UV protection,” said Phil Bucksbaum, a professor at SLAC and Stanford University and director of the Stanford PULSE Institute at SLAC. “You can even see these effects in plastic lawn furniture – after a couple of seasons it can become brittle and discolored simply due to the fact that the plastic was absorbing ultraviolet light all the time, and the way it absorbs sun results in damage to its chemical bonds.”

Catching Electrons in Action

Thymine and the other three DNA building blocks also strongly absorb ultraviolet light, which can trigger mutations and skin cancer, yet these molecules seem to get by with minimal damage. In 2014, a team led by Markus Guehr ­– then a SLAC senior staff scientist and now on the faculty of the University of Potsdam in Germany – reported that they had found the answer: The stretch-snap of a single bond and resulting energy-dissipating vibrations, which took place within 200 femtoseconds, or millionths of a billionth of a second after UV light exposure.

But what made the bond stretch? The team knew the answer had to involve electrons, which are responsible for forming, changing and breaking bonds between atoms. So they devised an ingenious way to catch the specific electron movements that trigger the protective response.

It relied on the fact that electrons don’t orbit an atom’s nucleus in neat concentric circles, like planets orbiting a sun, but rather in fuzzy clouds that take a different shape depending on how far they are from the nucleus. Some of these orbitals are in fact like a fuzzy sphere; others look a little like barbells or the start of a balloon animal. You can see examples here.

No image caption or credit, but there is a comment,
“I see the distribution in different orbitals. So if for example I take the S orbitals, they are all just a sphere. So wont the 2S orbital overlap with the 1S overlap, making the electrons in each orbital “meet” at some point? Or have I misunderstood something?”

Strong Signal Could Solve Long-Standing Debate

For this new experiment, the scientists hit thymine molecules with a pulse of UV laser light and tuned the energy of the LCLS X-ray laser pulses so they would home in on the response of the oxygen atom that’s at one end of the stretching, snapping bond.

The energy from the UV light excited one of the atom’s electrons to jump into a higher orbital. This left the atom in a sort of tippy state where just a little more energy would boost a second electron into a higher orbital; and that second jump is what sets off the protective response, changing the shape of the molecule just enough to stretch the bond.

The first jump, which was previously known to happen, is difficult to detect because the electron winds up in a rather diffuse orbital cloud, Guehr said. But the second, which had never been observed before, was much easier to spot because that electron ended up in an orbital with a distinctive shape that gave off a big signal.

“Although this was a very tiny electron movement, the signal kind of jumped out at us in the experiment,” Guehr said. “I always had a feeling this would be a strong transition, just intuitively, but when we saw this come in it was a special moment, one of the best moments an experimentalist can have.”

Settling a Longstanding Debate

Study lead author Thomas Wolf, an associate staff scientist at SLAC, said the results should settle a longstanding debate about how long after UV exposure the protective response kicks in: It happens 60 femtoseconds after UV light hits. This time span is important, he said, because the longer the atom spends in the tippy state between the first jump and the second, the more likely it is to undergo some sort of reaction that could damage the molecule.

Henrik Koch, a theorist at NTNU in Norway who was a guest professor at Stanford at the time, led the study with Guehr. He led the effort to model, understand and interpret what happened in the experiment, and he participated in it to an unusual extent, Guehr said.

“He is extremely experienced in applying theory to methodology development, and he had this curiosity to bring this to our experiment,” Guehr said. “He was so fascinated by this research that he did something completely untypical of a theorist – he came to LCLS, into the control room, and he wanted to see the data coming in. I found that completely amazing and very motivating. It turned out that some of my previous thinking was completely right but other aspects were completely wrong, and Henrik did the right theory at the right level so we could learn from it.”

See the full article here .

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SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the DOE’s Office of Science.

From SLAC: “New Research Finds a Missing Piece to High-Temperature Superconductor Mystery”

SLAC Lab

June 14, 2017
Mike Ross

This sketch shows how resonant inelastic X-ray scattering (RIXS) helps scientists understand the electronic behavior of copper oxide materials. An X-ray photon aimed at the sample (blue arrow) is absorbed by a copper atom, which then emits a new, lower-energy photon (red arrow) as it relaxes. The amount of momentum transferred and energy lost in this process can induce changes in the charge density waves thought to be important in high-temperature superconductivity. (Wei-Sheng/SLAC National Accelerator Laboratory)

An international team led by scientists from the Department of Energy’s SLAC National Accelerator Laboratory and Stanford University has detected new features in the electronic behavior of a copper oxide material that may help explain why it becomes a perfect electrical conductor – a superconductor – at relatively high temperatures.

Using an ultrahigh-resolution X-ray instrument in France, the researchers for the first time saw dynamic behaviors in the material’s charge density wave (CDW) – a pattern of electrons that resembles a standing wave – that lend support to the idea that these waves may play a role in high-temperature superconductivity.

Data taken at low (20 kelvins) and high (240 kelvins) temperatures showed that as the temperature increased, the CDW became more aligned with the material’s atomic structure. Remarkably, at the lower temperature, the CDW also induced an unusual increase in the intensity of the oxide’s atomic lattice vibrations, indicating that the dynamic CDW behaviors can propagate through the lattice.

“Previous research has shown that when the CDW is static, it competes with and diminishes superconductivity,” said co-author Wei-Sheng Lee, a SLAC staff scientist and investigator with the Stanford Institute for Materials and Energy Sciences (SIMES), which led the study published June 12 in Nature Physics. “If, on the other hand, the CDW is not static but fluctuating, theory tells us they may actually help form superconductivity.”

A Decades-long Search for an Explanation

The new result is the latest in a decades-long search by researchers worldwide for the factors that enable certain materials to become superconducting at relatively high temperatures.

Since the 1950s, scientists have known how certain metals and simple alloys become superconducting when chilled to within a few degrees of absolute zero: Their electrons pair up and ride waves of atomic vibrations that act like a virtual glue to hold the pairs together. Above a certain temperature, however, the glue fails as thermal vibrations increase, the electron pairs split up and superconductivity disappears.

In 1986, complex copper oxide materials were found to become superconducting at much higher – although still quite cold – temperatures. This discovery was so unexpected it caused a worldwide scientific sensation. By understanding and optimizing how these materials work, researchers hope to develop superconductors that work at room temperature and above.

At first, the most likely glue holding superconducting electron pairs together at higher temperatures seemed to be strong magnetic excitations created by interactions between electron spins. But in 2014, a theoretical simulation and experiments led by SIMES researchers concluded that these high-energy magnetic interactions are not the sole factor in copper oxide’s high-temperature superconductivity. An unanticipated CDW also appeared to be important.

The latest results continue the SIMES collaboration between experiment and theory. Building upon previous theories of how electron interactions with lattice vibrations can be probed with resonant inelastic X-ray scattering, or RIXS, the signature of CDW dynamics was finally identified, providing additional support for the CDW’s role in determining the electronic structure in superconducting copper oxides.

The Essential New Tool: RIXS

The new results are enabled by the development of more capable instruments employing RIXS. Now available at ultrahigh resolution at the European Synchrotron Radiation Facility (ESRF) in France, where the team performed this experiment, RIXS will also be an important feature of SLAC’s upgraded Linac Coherent Light Source X-ray free-electron laser, LCLS-II.

ESRF. Grenoble, France

SLAC LCLS-II

The combination of ultrahigh energy resolution and a high pulse repetition rate at LCLS-II will enable researchers to see more detailed CDW fluctuations and perform experiments aimed at revealing additional details of its behavior and links to high-temperature superconductivity. Most importantly, researchers at LCLS-II will be able to use ultrafast light-matter interactions to control CDW fluctuations and then take femtosecond-timescale snapshots of them.

RIXS involves illuminating a sample with X-rays that have just enough energy to excite some electrons deep inside the target atoms to jump up into a specific higher orbit. When the electrons relax back down into their previous positions, a tiny fraction of them emit X-rays that carry valuable atomic-scale information about the material’s electronic and magnetic configuration that is thought to be important in high-temperature superconductivity.

“To date, no other technique has seen evidence of propagating CDW dynamics,” Lee said.

RIXS was first demonstrated in the mid-1970s [Physical Review Letters], but it could not obtain useful information to address key problems until 2007, when Giacomo Ghiringhelli, Lucio Braicovich at Milan Polytechnic in Italy and colleagues at Swiss Light Source made a fundamental change that improved its energy resolution to a level where significant details became visible – technically speaking to about 120 milli-electronvolts (meV) at the relevant X-ray wavelength, which is called a copper L edge. The new RIXS instrument at ESRF is three times better, routinely attaining an energy resolution down to 40 meV. Since 2014, the Milan group has collaborated with SLAC and Stanford scientists in their RIXS research.

“The new ultrahigh resolution RIXS makes a huge difference,” Lee said. “It can show us previously invisible details.”

Other researchers involved in this result were from Milan Polytechnic, European Synchrotron Radiation Facility, Japan’s National Institute of Advanced Industrial Science and Technology and Italy’s National Research Council Institute for Superconductors, Oxides and Other Innovative Materials and Devices (CNR-SPIN). Funding for this research came from the DOE Office of Science.

See the full article here .

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SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the DOE’s Office of Science.

From BNL: “X-ray Study Reveals Way to Control Molecular Vibrations that Transmit Heat”

Brookhaven Lab

June 6, 2017
Karen McNulty Walsh
kmcnulty@bnl.gov
(631) 344-8350

Peter Genzer
genzer@bnl.gov
(631) 344-3174

Findings open new pathway for “tuning” materials to ease or insulate against the flow of heat, sound, and other forms of energy.

Brookhaven Lab members of the research team at the IXS beamline of the National Synchrotron Light Source II, left to right: Dima Bolmatov, Alessandro Cunsolo, Mikhail Zhernenkov, Ronald Pindak (sitting), Alexei Suvorov (sitting), and Yong Cai. The circular track accommodates utility cables and allows the arm housing the detectors to move to different locations to select the scattering angle for the measurement.

Scientists at the U.S. Department of Energy’s (DOE) Brookhaven National Laboratory have developed a new way to track dynamic molecular features in soft materials, including the high-frequency molecular vibrations that transmit waves of heat, sound, and other forms of energy. Controlling these vibrational waves in soft materials such as polymers or liquid crystal compounds could lead to a range of energy-inspired innovations—from thermal and acoustic insulators, to ways to convert waste heat into electricity, or light into mechanical motion.

In a paper just published in Nano Letters, the scientists describe using the newly constructed inelastic x-ray scattering (IXS) beamline at the National Synchrotron Light Source II (NSLS-II), which has unprecedented energy resolution, to monitor the propagation of vibrations through a liquid crystal compound in three different phases.

BNL NSLS-II

Their findings show that the nanoscale structural changes that occur with increasing temperature—as the liquid crystals become less ordered—dramatically disrupt the flow of vibrational waves. Thus choosing or changing the “phase,” or arrangement of molecules, could control the vibrations and the flow of energy.

“By tuning the structure, we can change the dynamic properties of this material,” said Brookhaven physicist Dima Bolmatov, the paper’s lead author.

The technique could also be used to study dynamic processes in other soft systems such as biological membranes or any kind of complex fluid.

“For example, we could look at how the lipid molecules in a cell membrane cooperate with each other to create tiny porous regions where even smaller molecules, like oxygen or carbon dioxide, can pass through—to see how gas exchange operates in gills and lungs,” Bolmatov said.

The ability to track such fast dynamic properties would not be possible without the unique capabilities of NSLS-II—a DOE Office of Science User Facility at Brookhaven Lab. NSLS-II produces extremely bright x-rays for studies in a wide range of scientific fields.

At the IXS beamline, scientists bombard samples with these x-rays and measure the energy they give up or gain with a precision to within two thousandths of an electron volt, as well as the angle at which they scatter off the sample—even at very small angles.

The energy exchange tells us how much energy it took to make some molecules vibrate in a wave-like motion. The scattering angle probes the vibrations propagating over different length scales inside the sample—from nearly a single molecule to tens of nanometers. The new IXS beamline at NSLS-II can resolve those length scales with unprecedented precision,” said Yong Cai, the lead scientist of the IXS beamline.

“These two parameters—the scattering angle and the energy—have never before been so well measured in soft materials. So the technical properties of this beamline enable us to precisely locate the vibrations and track their propagation in different directions over different length scales—even in materials that lack a well-ordered solid structure,” he added.

The colorful scattering pattern at left reveals molecular level structural information about the layered smectic phase of a liquid crystal material. The inner arcs indicate that the molecules are arrayed in ordered layers with regular spacing, while the outer arcs indicate there is still liquid-like mobility within the layers. The graph (top, right) represents inelastic x-ray scattering measurements from this smectic phase. Each peak (pink, orange, purple) represents a unique vibrational motion moving through the material, where the two “bumps” that make up each peak represent the energy gained or lost by the vibration. The purple and orange vibrations match the frequency of sound waves while the third, pink, vibration is linked to the tilt of the molecules (bottom, right). The out-of-phase rocking back-and-forth of these molecules matches the frequency of infrared light (heat).

In the liquid crystal study, the Brookhaven Lab scientists and their collaborators at Kent State University and the University at Albany made measurements at three different temperatures as the material went from an ordered, crystalline phase through transitions to a less-ordered “smectic” state, and finally an “isotropic” liquid. They easily detected the propagation of vibrational waves through the most ordered phase, and showed that the emergence of disorder “killed” the propagation of low energy “acoustic shear” vibrations. Acoustic shear vibrations are associated with a compression of the molecules in a direction perpendicular to the direction of propagation.

“Knowing where the dynamic boundary is—between the material behaving like an ordered solid and a disordered soft material—gives us a way to control the transmission of energy at the nanoscale,” Bolmatov said.

In the “smectic” phase, the scientists also observed a vibration that was associated instead with molecular tilt. This type of vibration can interact with light and absorb it because the terahertz frequency of the vibrations matches the frequency of infrared light or heat waves. So changing the material properties can control the way these forms of energy move through the material. Those changes can be achieved by changing the temperature of the material, as was done in this experiment, but also by applying external electric or magnetic fields, Bolmatov said.

This paves the way for new so-called phononic or optomechanical applications, where sound or light is coupled with the mechanical vibrations. Such coupling makes it possible to control a material by applying external light and sound or vice versa.

“We’re all familiar with applications using the optical properties of liquid crystals in display screens,” Bolmatov said. “We’ve found new properties that can be controlled or manipulated for new kinds of applications.”

The team will continue studies of soft materials at IXS, including planned experiments with block copolymers, nanoparticle assemblies, lipid membranes, and other liquid crystals over the summer.

“The IXS beamline is also now opened to external users—including scientists interested in these and other soft materials and biological processes,” said Cai.

The research team included Dima Bolmatov, Mikhail Zhernenkov, Alexey Suvorov, Ronald Pindak, Yong Cai, and Alessandro Cunsolo of NSLS-II, and Lewis Sharpnack, Deña M. Agra-Kooijman of Kent State University, and Satyendra Kumar of the University at Albany .

This research was supported by the DOE Office of Science.

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One of ten national laboratories overseen and primarily funded by the Office of Science of the U.S. Department of Energy (DOE), Brookhaven National Laboratory conducts research in the physical, biomedical, and environmental sciences, as well as in energy technologies and national security. Brookhaven Lab also builds and operates major scientific facilities available to university, industry and government researchers. The Laboratory’s almost 3,000 scientists, engineers, and support staff are joined each year by more than 5,000 visiting researchers from around the world.Brookhaven is operated and managed for DOE’s Office of Science by Brookhaven Science Associates, a limited-liability company founded by Stony Brook University, the largest academic user of Laboratory facilities, and Battelle, a nonprofit, applied science and technology organization.

From McGill: “A more sustainable way to refine metals”

McGill University

7Jun2017
Contact Information
Contact:
Prof. Jean-Philippe Lumb
jean-philip.lumb@mcgill.ca
514 398-4201

Secondary Contact Information
Contact:
Chris Chipello
christopher.chipello@mcgill.ca

New method could reduce environmental impact of extracting metals from raw materials and post-consumer electronics.

Strategy for reducing the environmental impact of a refining process: replace hazardous chemicals with more benign and recyclable compounds. CREDIT: Michael J. Krause (Western University)

A team of chemists in Canada has developed a way to process metals without using toxic solvents and reagents. The system, which also consumes far less energy than conventional techniques, could greatly shrink the environmental impact of producing metals from raw materials or from post-consumer electronics.

“At a time when natural deposits of metals are on the decline, there is a great deal of interest in improving the efficiency of metal refinement and recycling, but few disruptive technologies are being put forth,” says Jean-Philip Lumb, an associate professor in McGill University’s Department of Chemistry. “That’s what makes our advance so important.

The discovery stems from a collaboration between Lumb and Tomislav Friščić at McGill in Montreal, and Kim Baines of Western University in London, Ont. In an article published recently in Science Advances, the researchers outline an approach that uses organic molecules, instead of chlorine and hydrochloric acid, to help purify germanium, a metal used widely in electronic devices. Laboratory experiments by the researchers have shown that the same technique can be used with other metals, including zinc, copper, manganese and cobalt.

The research could mark an important milestone for the “green chemistry” movement, which seeks to replace toxic reagents used in conventional industrial manufacturing with more environmentally friendly alternatives. Most advances in this area have involved organic chemistry – the synthesis of carbon-based compounds used in pharmaceuticals and plastics, for example.

“Applications of green chemistry lag far behind in the area of metals,” Lumb says. “Yet metals are just as important for sustainability as any organic compound. For example, electronic devices require numerous metals to function.”

Taking a page from biology

There is no single ore rich in germanium, so it is generally obtained from mining operations as a minor component in a mixture with many other materials. Through a series of processes, that blend of matter can be reduced to germanium and zinc.

“Currently, in order to isolate germanium from zinc, it’s a pretty nasty process,” Baines explains. The new approach developed by the McGill and Western chemists “enables you to get germanium from zinc, without those nasty processes.”

To accomplish this, the researchers took a page from biology. Lumb’s lab for years has conducted research into the chemistry of melanin, the molecule in human tissue that gives skin and hair their color. Melanin also has the ability to bind to metals. “We asked the question: ‘Here’s this biomaterial with exquisite function, would it be possible to use it as a blueprint for new, more efficient technologies?’”

The scientists teamed up to synthesize a molecule that mimics some of the qualities of melanin. In particular, this “organic co-factor” acts as a mediator that helps to extract germanium at room temperature, without using solvents.

Using solvent-free mechanochemical techniques, milling jars containing stainless-steel balls are shaken at high speeds to promote chemical reactions. CREDIT: Michael Brand (University of Cardiff) and Jean-Louis Do (McGill University)

Next step: industrial scale

The system also taps into Friščić’s expertise in mechanochemistry, an emerging branch of chemistry that relies on mechanical force – rather than solvents and heat – to promote chemical reactions. Milling jars containing stainless-steel balls are shaken at high speeds to help purify the metal.

“This shows how collaborations naturally can lead to sustainability-oriented innovation,” Friščić says. “Combining elegant new chemistry with solvent-free mechanochemical techniques led us to a process that is cleaner by virtue of circumventing chlorine-based processing, but also eliminates the generation of toxic solvent waste”

The next step in developing the technology will be to show that it can be deployed economically on industrial scales, for a range of metals.

“There’s a tremendous amount of work that needs to be done to get from where we are now to where we need to go,” Lumb says. “But the platform works on many different kinds of metals and metal oxides, and we think that it could become a technology adopted by industry. We are looking for stakeholders with whom we can partner to move this technology forward.”

Funding for the research was provided by the Natural Sciences and Engineering Research Council of Canada, the National Natural Science Foundation of China, the Soochow University-Western University Center for Synchrotron Radiation Research, and the Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University.

“A chlorine-free protocol for processing germanium,” Martin Glavinović et al., Science Advances, 5 May 2017. DOI: 10.1126/sciadv.1700149 http://advances.sciencemag.org/content/3/5/e1700149

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All about McGill

With some 300 buildings, more than 38,500 students and 250,000 living alumni, and a reputation for excellence that reaches around the globe, McGill has carved out a spot among the world’s greatest universities.
Founded in Montreal, Quebec, in 1821, McGill is a leading Canadian post-secondary institution. It has two campuses, 11 faculties, 11 professional schools, 300 programs of study and some 39,000 students, including more than 9,300 graduate students. McGill attracts students from over 150 countries around the world, its 8,200 international students making up 21 per cent of the student body.

From NIST: “Nanocollaboration Leads to Big Things”

NIST

May 12, 2017 [Nothing like being timely getting into social media.]

Ben Stein
benjamin.stein@nist.gov
(301) 975-2763

Entrance to NIST’s Advanced Measurement Laboratory in Gaithersburg, Maryland. Credit: Photo Courtesy HDR Architecture, Inc./Steve Hall Copyright Hedrich Blessing

Roche Sequencing Solutions engineer Juraj Topolancik was looking for a way to decode DNA from cancer patients in a matter of minutes.

Rajesh Krishnamurthy, a researcher with the startup company 3i Diagnostics, needed help in fabricating a key component of a device that rapidly identifies infection-causing bacteria.

Ranbir Singh, an engineer with GeneSiC Semiconductor Inc., in Dulles, Virginia, sought to construct and analyze a semiconductor chip that transmits voltages large enough to power electric cars and spacecraft.

These researchers all credit the NanoFab, located at the Center for Nanoscale Science and Technology (CNST) on the Gaithersburg, Maryland campus of the National Institute of Standards and Technology (NIST). The NanoFab provides cutting-edge nanotechnology capabilities for NIST scientists that is also accessible to outside users, with supplying the state-of-art tools, know-how and dependability to realize their goals.

Learn more about the CNST NanoFab, where scientists from government, academia and industry can use commercial, state-of-the-art tools at economical rates, and get help from dedicated, full-time technical support staff. Voices: David Baldwin (Great Ball of Light, Inc.), Elisa Williams (Scientific & Biomedical Microsystems), George Coles (Johns Hopkins Applied Physics Laboratory) and William Osborn (NIST).

When Krishnamurthy, whose company is based in Germantown, Maryland, needed an infrared filter for the bacteria-identifying chip, proximity was but one factor in reaching out to the NanoFab.

“Even more important was the level of expertise you have here,” he says. “The attention to detail and the trust we have in the staff is so important—we didn’t have to worry if they would do a good job, which gives us tremendous peace of mind,” Krishnamurthy notes.

The NanoFab also aided his project in another, unexpected way. Krishnamurthy had initially thought that the design for his company’s device would require a costly, highly customized silicon chip. But in reviewing design plans with engineers at the NanoFab, “they came up with a very creative way” to use a more standard, less expensive silicon wafer that would achieve the same goals, he notes.

“The impact in the short term is that we didn’t have to pay as much [to build and test] the device at the NanoFab, which matters quite a bit because we’re a start-up company,” says Krishnamurthy. “In the long run, this will be a huge factor in [enabling us to mass produce] the device, keeping our costs low because, thanks to the input from the NanoFab, the source material is not a custom material.”

Singh came to the NanoFab with a different mission. His company is developing a gallium nitride semiconductor device durable enough to transmit hundreds to thousands of volts without deteriorating. He relies on the NanoFab’s metal deposition tools and high-resolution lithography instruments to finish building and assess the properties of the device.

Semiconductor device, fabricated with the help of the NanoFab, designed to transmit high voltages.
Credit: GeneSiC Semiconductor Inc.

“Not only is there a wide diversity of tools, but within each task there are multiple technologies,” Singh adds.

For instance, he notes, technologies offered at the NanoFab for depositing exquisitely thin and highly uniform layers of metal—which Singh found crucial for making reliable electrical contacts—include both evaporation and sputtering, he says.

The wide range of metals available for deposition at the NanoFab, uncommon at other nanotech facilities, was another draw.

“We needed different metals compared to those commonly used on silicon wafers and the NanoFab provided those materials,” notes Singh.

Topolancik, the Roche Sequencing Solutions engineer, needed high precision etching and deposition tools to fabricate a device that may ultimately improve cancer treatment. His company‘s plan to rapidly sequence DNA from cancer patients could quickly determine if potential anti-cancer drugs and those already in use are producing the genetic mutations necessary to fight cancer.

“We want to know if the drug is working, and if not, to stop using it and change the treatment,” says Topolancik.

In the standard method to sequence the double-stranded DNA molecule, a strand is peeled off and resynthesized, base by base, with each base—cytosine, adenine, guanine and thymine—tagged with a different fluorescent label.

“It’s a very accurate but slow method,” says Topolancik.

Instead of peeling apart the molecule, Topolancik is devising a method to read DNA directly, a much faster process. Borrowing a technique from the magnetic recording industry, he sandwiches the DNA between two electrodes separated by a gap just nanometers in width.

Illustration of experiment to directly identify the base pairs of a DNA strand (denoted by A, C, T, G in graph). Tunneling current flows through DNA placed between two closely spaced electrodes. Different bases allow different amounts of current to flow, revealing the components of the DNA molecule.
Credit: J. Topolancik/Roche Sequencing Solutions

According to quantum theory, if the gap is small enough, electrons will spontaneously “tunnel” from one electrode to the other. In Topolancik’s setup, the tunneling electrons must pass through the DNA in order to reach the other electrode.

The strength of the tunneling current identifies the bases of the DNA trapped between the electrodes. It’s an extremely rapid process, but for the technique to work reliably, the electrodes and the gap between them must be fabricated with extraordinarily high precision.

That’s where the NanoFab comes in. To deposit layers of different metals just nanometers in thickness on a wafer, Topolancik relies on the NanoFab’s ion beam deposition tool. And to etch a pattern in those ultrathin, supersmooth layers without disturbing them—a final step in fabricating the electrodes—requires the NanoFab’s ion etching instrument.

“These are specialty tools that are not usually accessible in academic facilities, but here [at the NanoFab] you have full, 24/7 access to them,” says Topolancik. “And if a tool goes down, it gets fixed right away,” he adds. “People here care about you, they want you to succeed because that’s the mission of the NanoFab.” As a result, he notes, “I can get done here in two weeks what would take half a year any place else.”

Take a 360-degree walking tour of the CNST NanoFab in this video!

See the full article here.

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NIST Campus, Gaitherberg, MD, USA

NIST Mission, Vision, Core Competencies, and Core Values

NIST’s mission

To promote U.S. innovation and industrial competitiveness by advancing measurement science, standards, and technology in ways that enhance economic security and improve our quality of life.
NIST’s vision

NIST will be the world’s leader in creating critical measurement solutions and promoting equitable standards. Our efforts stimulate innovation, foster industrial competitiveness, and improve the quality of life.
NIST’s core competencies

Measurement science
Rigorous traceability
Development and use of standards

NIST’s core values

NIST is an organization with strong values, reflected both in our history and our current work. NIST leadership and staff will uphold these values to ensure a high performing environment that is safe and respectful of all.

Perseverance: We take the long view, planning the future with scientific knowledge and imagination to ensure continued impact and relevance for our stakeholders.
Integrity: We are ethical, honest, independent, and provide an objective perspective.
Inclusivity: We work collaboratively to harness the diversity of people and ideas, both inside and outside of NIST, to attain the best solutions to multidisciplinary challenges.
Excellence: We apply rigor and critical thinking to achieve world-class results and continuous improvement in everything we do.

From SLAC: “New SLAC Theory Institute Aims to Speed Research on Exotic Materials at Light Sources”

SLAC Lab

April 11, 2017
Glennda Chui

A new institute at the Department of Energy’s SLAC National Accelerator Laboratory is using the power of theory to search for new types of materials that could revolutionize society – by making it possible, for instance, to transmit electricity over power lines with no loss.

The Theory Institute for Materials and Energy Spectroscopies (TIMES) focuses on improving experimental techniques and speeding the pace of discovery at West Coast X-ray facilities operated by SLAC and by Lawrence Berkeley National Laboratory, its DOE sister lab across the bay.

But the institute aims to have a much broader impact on studies aimed at developing new materials for energy and other technological applications by making the tools it develops available to scientists around the world.

TIMES opened in August 2016 as part of the Stanford Institute for Materials and Energy Sciences (SIMES), a DOE-funded institute operated jointly with Stanford.

Materials that Surprise

“We’re interested in materials with remarkable properties that seem to emerge out of nowhere when you arrange them in particular ways or squeeze them down into a single, two-dimensional layer,” says Thomas Devereaux, a SLAC professor of photon science who directs both TIMES and SIMES.

This general class of materials is known as “quantum materials.” Some of the best-known examples are high-temperature superconductors, which conduct electricity with no loss; topological insulators, which conduct electricity only along their surfaces; and graphene, a form of pure carbon whose superior strength, electrical conductivity and other surprising qualities derive from the fact that it’s just one layer of atoms thick.

In another research focus, Devereaux says, “We want to see what happens when you push materials far beyond their resting state – out of equilibrium, is the way we put it – by exciting them in various ways with pulses of X-ray light at facilities known as light sources.

“This tells you how materials will behave under realistic operating conditions, for instance in a lightweight airplane or a new type of battery. Understanding and controlling out-of-equilibrium behavior and learning how novel properties emerge in complex materials are two of the scientific grand challenges in our field, and light sources are ideal places to do this work.”

Joining Forces With Light Sources

A key part of the institute’s work is to use theory and computation to improve experimental techniques – especially X-ray spectroscopy, which probes the chemical composition and electronic structure of materials – in order to make research at light sources more productive.

“We are in a golden age of X-ray spectroscopy, in which many billions of dollars have been invested worldwide to develop new X-ray and neutron sources that allow us to study very small details and very fast processes in materials,” Devereaux says. “In fact, we are on the threshold of being able to control matter at a much deeper level than ever possible before.

“But while X-ray spectroscopy has a long history of collaboration between experimentalists and theorists, there has not been a companion theory institute anywhere. TIMES fills this gap. It aims to solidify collaboration and development of new methods and tools for theory relevant to this new landscape.”

Devereaux, a theorist who uses computation to study quantum materials, came to SLAC 10 years ago from the University of Waterloo in Canada to work more closely with researchers at three light sources – SLAC’s Stanford Synchrotron Radiation Lightsource (SSRL), Berkeley Lab’s Advanced Light Source (ALS) and the Linac Coherent Light Source (LCLS), the world’s first X-ray free-electron laser, which at the time was under construction at SLAC. Opened for research in 2009, LCLS gives scientists access to pulses a billion times brighter than any available before and that arrive up to 120 times per second, opening whole new avenues for research.

SLAC/SSRL

LBNL/ALS

SLAC LCLS

SLAC/LCLS II

With LCLS, Devereaux says, “It became clear that we had an unprecedented opportunity to study materials that have been pushed farther away from equilibrium than was ever possible before.”

Basic Questions and Practical Answers

The DOE-funded theory institute has hired two staff scientists, Chunjing Jia and Das Pemmaraju, and works closely with SLAC staff scientists Brian Moritz and Hongchen Jiang and with a number of scientists at the three light sources.

“We have two main goals,” Jia says. “One is to use X-ray spectroscopy and other techniques to look at practical materials, like the ones in batteries – to study the charging and discharging process and see how the structure of the battery changes, for instance. The second is to understand the fundamental underlying physics principles that govern the behavior of materials.”

Eventually, she added, theorists want to understand those physics principles so well that they can predict the results of high-priority experiments at facilities that haven’t even been built yet – for instance at LCLS-II, a major upgrade to LCLS that will add a much brighter X-ray laser beam that fires up to a million pulses per second. These predictions have the potential to make experiments at new facilities much more productive and efficient.

Running Experiments in Supercomputers

Theoretical work can involve a lot of math and millions of hours of supercomputer time, as theorists struggle to clarify how the fundamental laws of quantum mechanics apply to the materials they are investigating, Pemmaraju says.

“We use these laws in a form that can be simulated on a computer to make predictions about new materials and their properties,” he says. “The full richness and complexity of the theory are still being discovered, and its equations can only be solved approximately with the aid of supercomputers.”

Jia adds that you can think of these computer simulations as numerical experiments – working “in silico,” rather than at a lab bench. By simulating what’s going on in a material, scientists can decide which of all the experimental options are the best ones, saving both time and money.

The institute’s core research team includes theorists Joel Moore of the University of California, Berkeley and John Rehr of the University of Washington. Rehr is the developer of FEFF, an efficient and widely accessible software code that is used by the X-ray light source community worldwide. Devereaux says the plan is to establish a center for FEFF within the institute, which will serve as a home for its further development and for making those advances widely available to theorists and experimentalists at various levels of sophistication.

TIMES and SIMES are funded by the DOE Office of Science, and the three light sources – ALS, SSRL and LCLS – are DOE Office of Science User Facilities.

See the full article here .

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SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the DOE’s Office of Science.

From Stanford: “Stanford scientist’s new approach may accelerate design of high-power batteries”

Stanford University

April 6, 2017
Danielle Torrent Tucker

Electric vehicles plug in to charging stations. New research may accelerate discovery of materials used in electrical storage devices, such as car batteries. (Image credit: Shutterstock)

In work published this week in Applied Physics Letters, the researchers describe a mathematical model for designing new materials for storing electricity. The model could be a huge benefit to chemists and materials scientists, who traditionally rely on trial and error to create new materials for batteries and capacitors. Advancing new materials for energy storage is an important step toward reducing carbon emissions in the transportation and electricity sectors.

“The potential here is that you could build batteries that last much longer and make them much smaller,” said study co-author Daniel Tartakovsky, a professor in the School of Earth, Energy & Environmental Sciences. “If you could engineer a material with a far superior storage capacity than what we have today, then you could dramatically improve the performance of batteries.”

Lowering a barrier

One of the primary obstacles to transitioning from fossil fuels to renewables is the ability to store energy for later use, such as during hours when the sun is not shining in the case of solar power. Demand for cheap, efficient storage has increased as more companies turn to renewable energy sources, which offer significant public health benefits.

Tartakovsky hopes the new materials developed through this model will improve supercapacitors, a type of next-generation energy storage that could replace rechargeable batteries in high-tech devices like cellphones and electric vehicles. Supercapacitors combine the best of what is currently available for energy storage – batteries, which hold a lot of energy but charge slowly, and capacitors, which charge quickly but hold little energy. The materials must be able to withstand both high power and high energy to avoid breaking, exploding or catching fire.

“Current batteries and other storage devices are a major bottleneck for transition to clean energy,” Tartakovsky said. “There are many people working on this, but this is a new approach to looking at the problem.”

The types of materials widely used to develop energy storage, known as nanoporous materials, look solid to the human eye but contain microscopic holes that give them unique properties. Developing new, possibly better nanoporous materials has, until now, been a matter of trial and error – arranging minuscule grains of silica of different sizes in a mold, filling the mold with a solid substance and then dissolving the grains to create a material containing many small holes. The method requires extensive planning, labor, experimentation and modifications, without guaranteeing the end result will be the best possible option.

“We developed a model that would allow materials chemists to know what to expect in terms of performance if the grains are arranged in a certain way, without going through these experiments,” Tartakovsky said. “This framework also shows that if you arrange your grains like the model suggests, then you will get the maximum performance.”

Beyond energy

Energy is just one industry that makes use of nanoporous materials, and Tartakovsky said he hopes this model will be applicable in other areas, as well.

“This particular application is for electrical storage, but you could also use it for desalination, or any membrane purification,” he said. “The framework allows you to handle different chemistry, so you could apply it to any porous materials that you design.”

Tartakovsky’s mathematical modeling research spans neuroscience, urban development, medicine and more. As an Earth scientist and professor of energy resources engineering, he is an expert in the flow and transport of porous media, knowledge that is often underutilized across disciplines, he said. Tartakovsky’s interest in optimizing battery design stemmed from collaboration with a materials engineering team at the University of Nagasaki in Japan.

“This Japanese collaborator of mine had never thought of talking to hydrologists,” Tartakovsky said. “It’s not obvious unless you do equations – if you do equations, then you understand that these are similar problems.”

The lead author of the study, “Optimal design of nanoporous materials for electrochemical devices,” is Xuan Zhang, Tartakovsky’s former PhD student at the University of California, San Diego. The research was supported by the Defense Advanced Research Projects Agency and the National Science Foundation.

See the full article here .

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Leland and Jane Stanford founded the University to “promote the public welfare by exercising an influence on behalf of humanity and civilization.” Stanford opened its doors in 1891, and more than a century later, it remains dedicated to finding solutions to the great challenges of the day and to preparing our students for leadership in today’s complex world. Stanford, is an American private research university located in Stanford, California on an 8,180-acre (3,310 ha) campus near Palo Alto. Since 1952, more than 54 Stanford faculty, staff, and alumni have won the Nobel Prize, including 19 current faculty members