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  • richardmitnick 9:50 am on April 24, 2019 Permalink | Reply
    Tags: "Capturing the behavior of single-atom catalysts on the move", , , , SLAC Stanford SSRL,   

    From SLAC National Accelerator Lab: “Capturing the behavior of single-atom catalysts on the move” 

    From SLAC National Accelerator Lab

    April 23, 2019
    Glennda Chui

    1
    A new study precisely controlled the attachment of platinum atoms (white balls) to a titanium dioxide surface (latticework of red and blue balls). It found that their positions varied from being deeply embedded in the surface (lower left) to standing almost free of the surface (upper right). This change in position affected the atoms’ ability to catalyze a chemical reaction that converts carbon monoxide to carbon dioxide (upper right). (Greg Stewart, SLAC National Accelerator Laboratory)

    Scientists are excited by the prospect of stripping catalysts down to single atoms. Attached by the millions to a supporting surface, they could offer the ultimate in speed and specificity.

    Now researchers have taken an important step toward understanding single-atom catalysts by deliberately tweaking how they’re attached to the surfaces that support them – in this case the surfaces of nanoparticles. They attached one platinum atom to each nanoparticle and observed how changing the chemistry of the particle’s surface and the nature of the attachment affected how keen the atom was to catalyze reactions.

    Key experiments for the study took place at the Department of Energy’s SLAC National Accelerator Laboratory, and the results were reported in Nature Materials yesterday.

    “We believe this is the first time the reactivity of a metallic single-atom catalyst has been traced to a specific way of attaching it to a particular supporting structure. This study is also unique in systematically controlling that attachment,” said Simon R. Bare, a distinguished staff scientist at SLAC’s Stanford Synchrotron Radiation Lightsource (SSRL) and a co-author of the study.

    SLAC/SSRL

    “This is an important scientific breakthrough, and understanding on a fundamental level how the structure relates to the reactivity will ultimately allow us to design catalysts to be much more efficient. There is a huge number of people working on this problem.”

    Harsh treatment, good results

    Bare and other SLAC scientists were part of a previous study at SSRL [Nature Catalysis] that found that individual iridium atoms could catalyze a particular reaction up to 25 times more efficiently than the iridium nanoparticles used today, which contain 50 to 100 atoms.

    This latest study was led by Associate Professor Phillip Christopher of the University of California, Santa Barbara. It looked at individual atoms of platinum that were attached to separate nanoparticles of titanium dioxide in his lab. While this approach would probably not be practical in a chemical plant or in your car’s catalytic converter, it did give the research team exquisitely fine control of where the atoms were placed and of the environment immediately around them, Bare said.

    Researchers gave the nanoparticles chemical treatments – either harsh or mild – and used SSRL’s X-rays to observe how those treatments changed where and how the platinum atoms attached to the surface.

    Meanwhile, scientists at the University of California, Irvine directly observed the attachments and positions of the platinum atoms with electron microscopes, and researchers at UC-Santa Barbara measured how active the platinum atoms were in catalyzing reactions.

    Breaking through the surface

    A platinum atom has six binding sites where it can hook up with other atoms. In untreated nanoparticles, the atoms were buried in the surface and firmly bound to six oxygen atoms each; they had no free binding sites that could grab other atoms and start a catalytic reaction.

    In mildly treated particles, the platinum atoms emerged from the surface and were bound to just four oxygen atoms apiece, leaving them two free binding sites and the potential for more catalytic activity.

    And in harshly treated particles, the atoms clung to the surface by only two bonds, leaving four binding sites free. When the researchers tested the ability of the variously treated nanoparticles to catalyze a reaction where carbon monoxide combines with oxygen to form carbon dioxide – the same reaction that takes place in a car’s catalytic converter – this one came out on top, Bare said, with five times greater activity than the others.

    “While this study shows the importance of understanding the dynamic nature of catalysts,” Christopher said, “the next challenge will be to translate the findings to industrially relevant systems.”

    SSRL is a DOE Office of Science user facility. The changing positions of the platinum atoms on the particle surfaces were imaged and observed with transmission electron microscopy using state-of-the-art facilities recently established at the Irvine Materials Research Institute (IMRI) at UC-Irvine. Detailed experimental insights obtained in the study were correlated with predictions made by theorists at the University of Milano-Bicocca in Italy.

    See the full article here .


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    Please help promote STEM in your local schools.

    Stem Education Coalition

    SLAC/LCLS


    SLAC/LCLS II projected view


    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.

     
  • richardmitnick 9:19 am on April 9, 2019 Permalink | Reply
    Tags: Children’s Museum of Indianapolis, Mission Jurassic, , , SLAC Stanford SSRL   

    From SLAC National Accelerator Lab: “A mile-long graveyard of Jurassic fossils sparks a new international science collaboration” 

    From SLAC National Accelerator Lab

    March 28, 2019
    Ali Sundermier

    1
    Kimberly Calkins and Dallas Evans, lead curator of natural science and paleontology, with a sauropod femur at the upper sauropod quarry of The Jurassic Mile dig site. (Children’s Museum of Indianapolis)

    The Children’s Museum of Indianapolis announced plans this week for Mission Jurassic, a project that will support paleontological excavation of a fossil-rich plot of land in northern Wyoming. The project will bring together scientists from around the world, including the Department of Energy’s SLAC National Accelerator Laboratory, to reveal dramatic new secrets about the world of millions of years ago.

    “Mission Jurassic is a wonderful project because it’s not just an isolated fossil – it’s a suite of different organisms, including dinosaurs and plants, in a single location,” says SLAC scientist Nick Edwards. “We hope that through our involvement in this project, we will contribute some new information to the preservation, chemistry and maybe even the basic understanding of these extinct organisms, ancient ecosystems, and Earth history on the broader scale.”

    The Children’s Museum will serve as the Mission Jurassic leader. The project is made possible through a lead gift from Lilly Endowment Inc. Spearheaded by Phil Manning and Victoria Egerton of the University of Manchester in England, both scientists-in-residence at The Children’s Museum, more than 100 scientists from three countries will join forces to investigate the rare confluence of Jurassic Period fossils, trackways and fossilized plants. The site will provide clues that promise to tell a more complete story about the Jurassic Period.

    “We have been using SLAC’s Stanford Synchrotron Radiation Lightsource (SSRL) for over a decade to help map the subtle changes in chemistry that are a function of burial environments,” Manning says.

    SLAC SSRL Campus


    SLAC SSRL PEP collider map


    SLAC/SSRL

    “This work has real-world impact on how we might plan the long-term burial and disposal of waste in the 21st Century. We use the fossil record as a ‘hindsight laboratory’ that can better inform science on the mass transfer of compounds from the biosphere into the lithosphere”.

    The Jurassic Mile

    Project leaders are calling the fossil-rich, mile-square plot of land the Jurassic Mile. There are four main quarries within the multi-level, 640-acre site that offer a diverse assemblage of Morrison Formation articulated and semi-articulated dinosaurs. It has also yielded associated animals, fossil plants and dinosaur trackways of the Late Jurassic Period, 150 million years ago.

    Nearly 600 specimens weighing more than six tons have been collected from this site over the past two years, despite the fact that only a fraction of the site has been explored. They include the bones of an 80-foot-long sauropod (Brachiosaur) and 90-foot-long Diplodocid. A 6-foot-6-inch sauropod scapula (shoulder bone) and several blocks containing articulated bones are among the material collected during the 2018 field season. A 5-foot-1-inch femur was revealed at the announcement on March 25, 2019.

    Probing our world at the atomic level

    SLAC, a key partner working with the University of Manchester team, will shine bright X-rays onto the fossils at the SSRL, a DOE Office of Science user facility that produces X-ray beams perfectly tailored for probing the world at the atomic and molecular level. New imaging techniques being developed by the team have already resulted in multiple high-impact scientific publications.

    “Our primary instrument at SSRL is unique because it can do elemental imaging, which tells us where the elements are in fossils, and it can also do absorption spectroscopy, which tells us what chemical state they’re in,” says Uwe Bergmann, a distinguished staff scientist at SLAC. “It allows us to detect a wide range of important biological and geochemical elements, from light elements like phosphorous and sulfur all the way to the transition metals.”

    Specimens from the well-preserved fossil remains at the Jurassic Mile site will form the basis for a major expansion of The Children’s Museum of Indianapolis’ permanent Dinosphere exhibit that will add creatures from the Jurassic Period. The project is already utilizing cutting-edge science, from particle accelerators to some of the most powerful computers on the planet, to help resurrect the Jurassic dinosaurs and add momentum to the process of unearthing the lost world and forgotten lives.

    This article is based on a press release from The Children’s Museum of Indianapolis.

    From the press release, no image credits:

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    4

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition

    SLAC/LCLS


    SLAC/LCLS II projected view


    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.

     
  • richardmitnick 8:30 pm on February 21, 2019 Permalink | Reply
    Tags: , , , , Molecular ensemble, , , , PtPOP, , , SLAC Stanford SSRL,   

    From SLAC National Accelerator Lab: “Researchers watch molecules in a light-triggered catalyst ring ‘like an ensemble of bells’’ 

    From SLAC National Accelerator Lab

    February 21, 2019
    Ali Sundermier

    1
    Synchronized molecules
    When photocatalyst molecules absorb light, they start vibrating in a coordinated way, like an ensemble of bells. Capturing this response is a critical step towards understanding how to design molecules for the efficient transformation of light energy to high-value chemicals. (Gregory Stewart/SLAC National Accelerator Laboratory)

    A better understanding of these systems will aid in developing next-generation energy technologies.

    Photocatalysts ­– materials that trigger chemical reactions when hit by light – are important in a number of natural and industrial processes, from producing hydrogen for fuel to enabling photosynthesis.

    Now an international team has used an X-ray laser at the Department of Energy’s SLAC National Accelerator Laboratory to get an incredibly detailed look at what happens to the structure of a model photocatalyst when it absorbs light.

    The researchers used extremely fast laser pulses to watch the structure change and see the molecules vibrating, ringing “like an ensemble of bells,” says lead author Kristoffer Haldrup, a senior scientist at Technical University of Denmark (DTU). This study paves the way for deeper investigation into these processes, which could help in the design of better catalysts for splitting water into hydrogen and oxygen for next-generation energy technologies.

    “If we can understand such processes, then we can apply that understanding to developing molecular systems that do tricks like that with very high efficiency,” Haldrup says.

    The results published last week in Physical Review Letters.

    Molecular ensemble

    The platinum-based photocatalyst they studied, called PtPOP, is one of a class of molecules that scissors hydrogen atoms off various hydrocarbon molecules when hit by light, Haldrup says: “It’s a testbed – a playground, if you will – for studying photocatalysis as it happens.”

    At SLAC’S X-ray laser, the Linac Coherent Light Source (LCLS), the researchers used an optical laser to excite the platinum-containing molecules and then used X-rays to see how these molecules changed their structure after absorbing the visible photons.

    SLAC/LCLS

    The extremely short X-ray laser pulses allowed them to watch the structure change, Haldrup says.

    The researchers used a trick to selectively “freeze” some of the molecules in their vibrational motion, and then used the ultrashort X-ray pulses to capture how the entire ensemble of molecules evolved in time after being hit with light. By taking these images at different times they can stitch together the individual frames like a stop-motion movie. This provided them with detailed information about molecules that were not hit by the laser light, offering insight into the ultrafast changes occurring in the molecules when they are at their lowest energy.

    Swimming in harmony

    Even before the light hits the molecules, they are all vibrating but out of sync with one another. Kelly Gaffney, co-author on this paper and director of SLAC’s Stanford Synchrotron Radiation Lightsource, likens this motion to swimmers in a pool, furiously treading water.

    SLAC SSRL Campus


    SLAC/SSRL


    SLAC/SSRL

    When the optical laser hits them, some of the molecules affected by the light begin moving in unison and with greater intensity, switching from that discordant tread to synchronized strokes. Although this phenomenon has been seen before, until now it was difficult to quantify.

    “This research clearly demonstrates the ability of X-rays to quantify how excitation changes the molecules,” Gaffney says. “We can not only say that it’s excited vibrationally, but we can also quantify it and say which atoms are moving and by how much.”

    Predictive chemistry

    To follow up on this study, the researchers are investigating how the structures of PtPOP molecules change when they take part in chemical reactions. They also hope to use the information they gained in this study to directly study how chemical bonds are made and broken in similar molecular systems.

    “We get to investigate the very basics of photochemistry, namely how exciting the electrons in the system leads to some very specific changes in the overall molecular structure,” says Tim Brandt van Driel, a co-author from DTU who is now a scientist at LCLS. “This allows us to study how energy is being stored and released, which is important for understanding processes that are also at the heart of photosynthesis and the visual system.”

    A better understanding of these processes could be key to designing better materials and systems with useful functions.

    “A lot of chemical understanding is rationalized after the fact. It’s not predictive at all,” Gaffney says. “You see it and then you explain why it happened. We’re trying to move the design of useful chemical materials into a more predictive space, and that requires accurate detailed knowledge of what happens in the materials that already work.”

    LCLS and SSRL are DOE Office of Science user facilities. This research was supported by DANSCATT; the Independent Research Fund Denmark; the Icelandic Research Fund; the Villum Foundation; and the AMOS program within the Chemical Sciences, Geosciences and Biosciences Division of the DOE Office of Basic Energy Sciences.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition

    SLAC Campus
    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.

     
  • richardmitnick 10:13 am on January 8, 2019 Permalink | Reply
    Tags: , , , Infrared spectroscopy, , , SLAC Stanford SSRL,   

    From SLAC National Accelerator Lab: “Study shows single atoms can make more efficient catalysts” 

    From SLAC National Accelerator Lab

    January 7, 2019
    Glennda Chui

    1
    Scientists used a combination of four techniques, represented here by four incoming beams, to reveal in unprecedented detail how a single atom of iridium catalyzes a chemical reaction. (Greg Stewart/SLAC National Accelerator Laboratory)

    Detailed observations of iridium atoms at work could help make catalysts that drive chemical reactions smaller, cheaper and more efficient.

    Catalysts are chemical matchmakers: They bring other chemicals close together, increasing the chance that they’ll react with each other and produce something people want, like fuel or fertilizer.

    Since some of the best catalyst materials are also quite expensive, like the platinum in a car’s catalytic converter, scientists have been looking for ways to shrink the amount they have to use.

    Now scientists have their first direct, detailed look at how a single atom catalyzes a chemical reaction. The reaction is the same one that strips poisonous carbon monoxide out of car exhaust, and individual atoms of iridium did the job up to 25 times more efficiently than the iridium nanoparticles containing 50 to 100 atoms that are used today.

    The research team, led by Ayman M. Karim of Virginia Tech, reported the results in Nature Catalysis.

    “These single-atom catalysts are very much a hot topic right now,” said Simon R. Bare, a co-author of the study and distinguished staff scientist at the Department of Energy’s SLAC National Accelerator Laboratory, where key parts of the work took place. “This gives us a new lens to look at reactions through, and new insights into how they work.”

    Karim added, “To our knowledge, this is the first paper to identify the chemical environment that makes a single atom catalytically active, directly determine how active it is compared to a nanoparticle, and show that there are very fundamental differences – entirely different mechanisms – in the way they react.”

    Is smaller really better?

    Catalysts are the backbone of the chemical industry and essential to oil refining, where they help break crude oil into gasoline and other products. Today’s catalysts often come in the form of nanoparticles attached to a surface that’s porous like a sponge – so full of tiny holes that a single gram of it, unfolded, might cover a basketball court. This creates an enormous area where millions of reactions can take place at once. When gas or liquid flows over and through the spongy surface, chemicals attach to the nanoparticles, react with each other and float away. Each catalyst is designed to promote one specific reaction over and over again.

    But catalytic reactions take place only on the surfaces of nanoparticles, Bare said, “and even though they are very small particles, the expensive metal on the inside of the nanoparticle is wasted.”

    Individual atoms, on the other hand, could offer the ultimate in efficiency. Each and every atom could act as a catalyst, grabbing chemical reactants and holding them close together until they bond. You could fit a lot more of them in a given space, and not a speck of precious metal would go to waste.

    Single atoms have another advantage: Unlike clusters of atoms, which are bound to each other, single atoms are attached only to the surface, so they have more potential binding sites available to perform chemical tricks – which in this case came in very handy.

    Research on single-atom catalysts has exploded over the past few years, Karim said, but until now no one has been able to study how they function in enough detail to see all the fleeting intermediate steps along the way.

    Grabbing some help

    To get more information, the team looked at a simple reaction where single atoms of iridium split oxygen molecules in two, and the oxygen atoms then react with carbon monoxide to create carbon dioxide.

    They used four approaches­ – infrared spectroscopy, electron microscopy, theoretical calculations and X-ray spectroscopy with beams from SLAC’s Stanford Synchrotron Radiation Lightsource (SSRL) – to attack the problem from different angles, and this was crucial for getting a complete picture.

    SLAC/SSRL

    SLAC SSRL Campus

    “It’s never just one thing that gives you the full answer,” Bare said. “It’s always multiple pieces of the jigsaw puzzle coming together.”

    The team discovered that each iridium atom does, in fact, perform a chemical trick that enhances its performance. It grabs a single carbon monoxide molecule out of the passing flow of gas and holds onto it, like a person tucking a package under their arm. The formation of this bond triggers tiny shifts in the configuration of the iridium atom’s electrons that help it split oxygen, so it can react with the remaining carbon monoxide gas and convert it to carbon dioxide much more efficiently.

    More questions lie ahead: Will this same mechanism work in other catalytic reactions, allowing them to run more efficiently or at lower temperatures? How do the nature of the single-atom catalyst and the surface it sits on affect its binding with carbon monoxide and the way the reaction proceeds?

    The team plans to return to SSRL in January to continue the work.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition

    SLAC Campus
    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.

     
  • richardmitnick 10:11 am on November 2, 2018 Permalink | Reply
    Tags: "In materials hit with light", , , individual atoms and vibrations take disorderly paths", , , , SLAC Stanford SSRL,   

    From SLAC Lab: “In materials hit with light, individual atoms and vibrations take disorderly paths” 


    From SLAC Lab

    November 1, 2018
    Glennda Chui

    1
    Two studies with a new X-ray laser technique reveal for the first time how individual atoms and vibrations respond when a material is hit with light. Their surprisingly unpredictable behavior has profound implications for designing and controlling materials. (Greg Stewart/SLAC National Accelerator Laboratory)

    Revealed for the first time by a new X-ray laser technique, their surprisingly unruly response has profound implications for designing and controlling materials.

    Hitting a material with laser light sends vibrations rippling through its latticework of atoms, and at the same time can nudge the lattice into a new configuration with potentially useful properties – turning an insulator into a metal, for instance.

    Until now, scientists assumed this all happened in a smooth, coordinated way. But two new studies show it doesn’t: When you look beyond the average response of atoms and vibrations to see what they do individually, the response, they found, is disorderly.

    Atoms don’t move smoothly into their new positions, like band members marching down a field; they stagger around like partiers leaving a bar at closing time.

    And laser-triggered vibrations don’t simply die out; they trigger smaller vibrations that trigger even smaller ones, spreading out their energy in the form of heat, like a river branching into a complex network of streams and rivulets.

    This unpredictable behavior at a tiny scale, measured for the first time with a new X-ray laser technique at the Department of Energy’s SLAC National Accelerator Laboratory, will have to be taken into account from now on when studying and designing new materials, the researchers said – especially quantum materials with potential applications in sensors, smart windows, energy storage and conversion and super-efficient electrical conductors.

    Two separate international teams, including researchers at SLAC and Stanford University who developed the technique, reported the results of their experiments Sept. 20 in Physical Review Letters and today in Science.

    “The disorder we found is very strong, which means we have to rethink how we study all of these materials that we thought were behaving in a uniform way,” said Simon Wall, an associate professor at the Institute of Photonic Sciences in Barcelona and one of three leaders of the study reported in Science. “If our ultimate goal is to control the behavior of these materials so we can switch them back and forth from one phase to another, it’s much harder to control the drunken choir than the marching band.”

    Lifting the haze

    The classic way to determine the atomic structure of a molecule, whether from a manmade material or a human cell, is to hit it with X-rays, which bounce off and scatter into a detector. This creates a pattern of bright dots, called Bragg peaks, that can be used to reconstruct how its atoms are arranged.

    SLAC’s Linac Coherent Light Source (LCLS), with its super-bright and ultrafast X-ray laser pulses, has allowed scientists to determine atomic structures in ever more detail.

    SLAC/LCLS

    They can even take rapid-fire snapshots of chemical bonds breaking, for instance, and string them together to make “molecular movies.”

    About a dozen years ago, David Reis, a professor at SLAC and Stanford and investigator at the Stanford Institute for Materials and Energy Sciences (SIMES), wondered if a faint haze between the bright spots in the detector – 10,000 times weaker than those bright spots, and considered just background noise – could also contain important information about rapid changes in materials induced by laser pulses.

    He and SIMES scientist Mariano Trigo went on to develop a technique called “ultrafast diffuse scattering” that extracts information from the haze to get a more complete picture of what’s going on and when.

    The two new studies represent the first time the technique has been used to observe details of how energy dissipates in materials and how light triggers a transition from one phase, or state, of a material to another, said Reis, who along with Trigo is a co-author of both papers. These responses are interesting both for understanding the basic physics of materials and for developing applications that use light to switch the properties of materials on and off or convert heat to electricity, for instance.

    “It’s sort of like astronomers studying the night sky,” said Olivier Delaire, an associate professor at Duke University who helped lead one of the studies. “Previous studies could only see the brightest stars visible to the naked eye. But with the ultrabright and ultrafast X-ray pulses, we were able to see the faint and diffuse signals of the Milky Way galaxy between them.”

    Tiny bells and piano strings

    In the study published in Physical Review Letters, Reis and Trigo led a team that investigated vibrations called phonons that rattle the atomic lattice and spread heat through a material.

    The researchers knew going in that phonons triggered by laser pulses decay, releasing their energy throughout the atomic lattice. But where does all that energy go? Theorists proposed that each phonon must trigger other, smaller phonons, which vibrate at higher frequencies and are harder to detect and measure, but these had never been seen in an experiment.

    To study this process at LCLS, the team hit a thin film of bismuth with a pulse of optical laser light to set off phonons, followed by an X-ray laser pulse about 50 quadrillionths of a second later to record how the phonons evolved. The experiments were led by graduate student Tom Henighan and postdoctoral researcher Samuel Teitelbaum of the Stanford PULSE Institute.

    For the first time, Trigo said, they were able to observe and measure how the initial phonons distributed their energy over a wider area by triggering smaller vibrations. Each of those small vibrations emanated from a distinct patch of atoms, and the size of the patch – whether it contained 7 atoms, or 9, or 20 – determined the frequency of the vibration. It was much like how ringing a big bell sets smaller bells tinkling nearby, or how plucking a piano string sets other strings humming.

    “This is something we’ve been waiting years to be able to do, so we were excited,” Reis said. “It’s a measurement of something absolutely fundamental to modern solid-state physics, for everything from how heat flows in materials to even, in principle, how light-induced superconductivity emerges, and it could not have been done without an X-ray free-electron laser like LCLS.”

    A disorderly march

    The paper in Science describes LCLS experiments with vanadium dioxide, a well-studied material that can flip from being an insulator to an electrical conductor in just 100 quadrillionths of a second.

    Researchers already knew how to trigger this switch with very short, ultrafast pulses of laser light. But until now they could only observe the average response of the atoms, which seemed to shuffle into their new positions in an orderly way, said Delaire, who led the study with Wall and Trigo.

    The new round of diffuse scattering experiments at LCLS showed otherwise. By hitting the vanadium dioxide with an optical laser of just the right energy, the researchers were able to trigger a substantial rearrangement of the vanadium atoms. They did this more than 100 times per second while recording the movements of individual atoms with the LCLS X-ray laser. They discovered that each atom followed an independent, seemingly random path to its new lattice position. Computer simulations by Duke graduate student Shan Yang backed up that conclusion.

    “Our findings suggest that disorder may play an important role in some materials,” the team wrote in the Science paper. While this may complicate efforts to control the way materials shift from one phase to another, they added, “it could ultimately provide a new perspective on how to control matter,” and even suggest a new way to induce superconductivity with light.

    In a commentary accompanying the report in Science, Andrea Cavalleri of Oxford University and the Max Planck Institute for the Structure and Dynamics of Matter said the results imply that molecular movies of atoms changing position over time don’t paint a complete picture of the microscopic physics involved.

    He added, “More generally, it is clear from this work that x-ray free electron lasers are opening up far more than what was envisaged when these machines were being planned, forcing us to reevaluate many old notions taken for granted up to now.”

    The study published in PRL also involved researchers from Imperial College London; Tyndall National Institute in Ireland; and the University of Michigan, Ann Arbor. Preliminary measurements were performed at SLAC’s Stanford Synchrotron Radiation Lightsource (SSRL). Major funding came from the DOE Office of Science.

    SLAC/SSRL

    The study published in Science also involved researchers at the Japan Synchrotron Radiation Research Institute and the DOE’s Oak Ridge National Laboratory. Calculations were performed using resources of the DOE’s National Energy Research Scientific Computing Center (NERSC), and computer simulations used resources of the Oak Ridge Leadership Computing Facility. Major funding came from the European Research Council under the European Union’s Horizon 2020 research and innovation program and from the DOE Office of Science.

    LCLS, SSRL and NERSC are DOE Office of Science user facilities.

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    SLAC Campus
    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.

     
  • richardmitnick 11:35 am on July 3, 2018 Permalink | Reply
    Tags: , , , SLAC Stanford SSRL,   

    From SLAC Lab: “X-Ray Experiment Confirms Theoretical Model for Making New Materials” 


    From SLAC Lab

    July 2, 2018
    Glennda Chui

    1
    In an experiment at SLAC, scientists loaded ingredients for making a material into a thin glass tube and used X-rays (top left) to observe the phases it went through as it was forming (shown in bubbles). The experiment verified theoretical predictions made by scientists at Berkeley Lab with the help of supercomputers (right). (Greg Stewart/SLAC National Accelerator Laboratory)

    By observing changes in materials as they’re being synthesized, scientists hope to learn how they form and come up with recipes for making the materials they need for next-gen energy technologies.

    Over the last decade, scientists have used supercomputers and advanced simulation software to predict hundreds of new materials with exciting properties for next-generation energy technologies.

    Now they need to figure out how to make them.

    To predict the best recipe for making a material, they first need a better understanding of how it forms, including all the intermediate phases it goes through along the way – some of which may be useful in their own right.

    Now experiments at the Department of Energy’s SLAC National Accelerator Laboratory have confirmed the predictive power of a new computational approach to materials synthesis. Researchers say that this approach, developed at the DOE’s Lawrence Berkeley National Laboratory, could streamline the creation of novel materials for solar cells, batteries and other sustainable technologies.

    “In the last 10 years, computational scientists have gotten really good at predicting the properties of new materials, but not so good at telling experimentalists like me how to make them,” said Michael Toney, a distinguished staff scientist at SLAC. “The theoretical framework developed at Berkeley Lab can help guide us in thinking about ways to synthesize and test these promising materials.”

    This team described their findings June 29 in Nature Communications.

    Metastable Materials

    “Most theoretical approaches are great for predicting the endpoints of a reaction – what chemicals you start with, and what material you get at the end,” said study co-author Laura Schelhas, an associate staff scientist with SLAC’s Applied Energy Program. “But other interesting materials that form along the reaction pathway are often overlooked.”

    These intermediate materials are said to exist in a state of metastability.

    “Materials always want to be in their lowest-energy phase or ground state,” Schelhas explained. “Materials in a metastable state are higher in energy and will eventually transition to the more stable ground state. A diamond, for example, is a metastable state of carbon that will revert to its ground state, graphite, over millions of years.”

    During synthesis, materials can crystallize into a series of metastable phases – some lasting only a few minutes, others persisting for hours. Some of these phases have properties that are potentially useful for technological applications. Others may block the formation of a material you want to make. Scientists want to isolate the useful phases and avoid creating the undesirable ones.

    Co-authors Wenhao Sun and Gerbrand Ceder at Berkeley Lab and Daniil Kitchaev of the Massachusetts Institute of Technology recently developed a theoretical model to predict which metastable phases a material will form during synthesis.

    “The key insight is to consider influences other than temperature and pressure that can affect a material’s formation,” Sun said. “For example, at a very small scale, surface energy is important, and impurities that materials take up from the surrounding environment can stabilize some types of crystalline structures. We developed a theory to quantify how these factors govern the formation of metastable phases, and then worked with SLAC to design an experiment to test it.”

    The experiment, conducted at SLAC’s Stanford Synchrotron Radiation Lightsource (SSRL), focused on manganese oxide, a compound whose formation can involve a variety of metastable crystalline structures. Some of these metastable structures are useful for battery applications or catalysis.

    SLAC/SSRL

    2
    Schematic representation of remnant metastability in a crystallization pathway. a Free-energy of three phases (supersaturated solution (gray), M (green), S (blue)) as a function of the surface-area-to-volume ratio, 1/R (R is a particle radius). The gray line corresponds to the free-energy of a supersaturated solution, green is a metastable phase M that is size-stabilized by a low surface energy (given by the slope), and blue is the bulk equilibrium phase S, with high surface energy. b Phase diagram in the 1/R axis created from the projection of lowest free-energy phases. c A multistage crystallization pathway (red arrow in a ) proceeds downhill in energy, but phase transformations are limited by nucleation. Crystal growth of M prior to the induction of S means M can grow into a size-regime where phase M is metastable. S will then nucleate, and quickly grow by consuming M via dissolution-reprecipitation. The characteristic length scale of size-driven phase transitions lies in the 2 nm–50 nm range. Nature Communications

    “Although manganese oxide has been widely studied, we still don’t have a good understanding of how to make specific metastable phases of the material,” Toney said. “Figuring out why certain recipes favor certain metastable structures will help us predict recipes for synthesizing not just this material, but others as well.”

    Theory vs. Experiment

    Sun and Schelhas designed an experiment to carefully manipulate a single ingredient in a recipe for making manganese oxide and track its effect on the formation of metastable crystals.

    SLAC scientists led by postdoctoral researcher Bor-Rong Chen used powerful X-ray beams at SSRL to observe the chemical reaction as it happened.

    “It’s pretty simple,” Schelhas said. “We load up manganese salts and other reaction materials into a small glass capillary, seal it and heat it. Then we shoot X-rays through the capillary while the reaction is occurring and watch the signal that reflects off the crystals. That signal allows us to determine the atomic structure of each metastable phase as it forms.”

    At first, the metastable phases identified by X-ray diffraction didn’t seem to match the theoretical predictions, Chen said.

    “We worked with the theorists at Berkeley Lab to retool the model,” she said, “and arrived at some explanations for why certain metastable phases might be skipped in a reaction, or why they might persist longer than we anticipated.”

    To continue developing their understanding of synthesis, the researchers plan to conduct experiments on more complicated materials.

    “This work marks only the initial steps in a much longer journey towards a predictive theory of materials synthesis,” Sun said. “Our goal is to build a powerful toolkit to design recipes for making exactly the materials we want.”

    The team also found that they could stop the reaction at the point where a metastable material has formed, which will make it possible to test those materials for desirable properties in future studies, Schelhas said.

    “We’re starting to push science into a new space in terms of understanding how you go about synthesis,” she added. “Predictive models have the potential to profoundly alter the way that materials design is done. That could greatly speed up the adoption of more advanced materials in areas like photovoltaics, batteries, thermoelectrics and a whole host of other sustainable technologies.”

    Other co-authors of the study are from the Colorado School of Mines and the DOE’s National Renewable Energy Laboratory.

    SSRL is a DOE Office of Science user facility. Funding for this work came from the Center for Next Generation of Materials Design, an Energy Frontier Research Center led by DOE’s National Renewable Energy Laboratory and funded by the DOE Office of Science.

    See the full article here .


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  • richardmitnick 2:06 pm on December 12, 2017 Permalink | Reply
    Tags: Electric car makers are intensely interested in lithium-rich battery cathodes that could significantly increase driving range, , Scientists Discover Path to Improving Game-Changing Battery Electrode, , SLAC Stanford SSRL   

    From SLAC: “Scientists Discover Path to Improving Game-Changing Battery Electrode” 


    SLAC Lab

    Electric car makers are intensely interested in lithium-rich battery cathodes that could significantly increase driving range. A new study opens a path to making them live up to their promise.

    1
    Electric car makers are intensely interested in lithium-rich battery cathodes that could significantly increase driving range. A new study opens a path to making them live up to their promise. (Stanford University/3Dgraphic)

    2
    SLAC and Stanford researchers at an SSRL beamline used for battery research. From left: SLAC staff scientists Apurva Mehta and Kevin Stone; Stanford graduate students Will Gent and Kipil Lim; and SLAC distinguished staff scientist Mike Toney. (Dawn Harmer/SLAC National Accelerator Laboratory)

    December 12, 2017
    If you add more lithium to the positive electrode of a lithium-ion battery – overstuff it, in a sense ­– it can store much more charge in the same amount of space, theoretically powering an electric car 30 to 50 percent farther between charges. But these lithium-rich cathodes quickly lose voltage, and years of research have not been able to pin down why – until now.

    After looking at the problem from many angles, researchers from Stanford University, two Department of Energy national labs and the battery manufacturer Samsung created a comprehensive picture of how the same chemical processes that give these cathodes their high capacity are also linked to changes in atomic structure that sap performance.

    “This is good news,” said William E. Gent, a Stanford University graduate student and Siebel Scholar who led the study. “It gives us a promising new pathway for optimizing the voltage performance of lithium-rich cathodes by controlling the way their atomic structure evolves as a battery charges and discharges.”

    Michael Toney, a distinguished staff scientist at SLAC National Accelerator Laboratory and a co-author of the paper, added, “It is a huge deal if you can get these lithium-rich electrodes to work because they would be one of the enablers for electric cars with a much longer range. There is enormous interest in the automotive community in developing ways to implement these, and understanding what the technological barriers are may help us solve the problems that are holding them back.”

    The team’s report appears today in Nature Communications.

    The researchers studied the cathodes with a variety of X-ray techniques at SLAC’s Stanford Synchrotron Radiation Lightsource (SSRL) and Lawrence Berkeley National Laboratory’s Advanced Light Source (ALS).

    SLAC/SSRL

    LBNL/ALS

    Theorists from Berkeley Lab’s Molecular Foundry, led by David Prendergast, were also involved, helping the experimenters understand what to look for and explain their results.

    The cathodes themselves were made by Samsung Advanced Institute of Technology using commercially relevant processes, and assembled into batteries similar to those in electric vehicles.

    “This ensured that our results represented an understanding of a cutting-edge material that would be directly relevant for our industry partners,” Gent said. As an ALS doctoral fellow in residence, he was involved in both the experiments and the theoretical modelling for the study.

    See the full article here .

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  • richardmitnick 10:37 am on November 29, 2017 Permalink | Reply
    Tags: , , Dnm1 proteins, , , SLAC Stanford SSRL, , UCLA bioengineers discover mechanism that regulates cells’ ‘powerhouses’   

    From UCLA Newsroom: “UCLA bioengineers discover mechanism that regulates cells’ ‘powerhouses’” 


    UCLA Newsroom

    November 27, 2017
    Matthew Chin

    1
    In this artist’s rendering, Dnm1 proteins surrounding a mitochondrion are breaking it up into two. Jaime de Anda/ACS Central Science.

    UCLA bioengineers and their colleagues have discovered a new perspective on how cells regulate the sizes of mitochondria, the parts of cells that provide energy, by cutting them into smaller units.

    The researchers wrote that this finding, demonstrated with yeast proteins, could eventually be used to help address human diseases associated with an imbalanced regulation of mitochondria size — for example, Alzheimer’s or Parkinson’s diseases. In addition, since having mitochondria that are too small or too large can potentially lead to incurable diseases, it is conceivable that the proteins responsible for this process could be potential targets for future therapies.

    The study was published in ACS Central Science and was led by UCLA bioengineering professor Gerard Wong.

    Inside the cell, mitochondria resemble the long balloons used to create balloon animals. If the mitochondria are too long, they can get tangled. Their sizes are known to be primarily regulated by two proteins, one of which breaks up longer mitochondria into smaller sizes. They are known as cells’ “powerhouses” as they convert chemical energy from food into a form useful for cells to perform all their functions.

    Keeping mitochondria at optimal sizes is important to cells’ health. An insufficient amount of the regulating protein, known as Dnm1, results in the mitochondria getting too long and tangled. Too much Dnm1 results in too many short mitochondria. In both cases, the mitochondria are rendered essentially ineffective as power providers for the cell. This situation could lead to neurodevelopmental disorders or neurodegenerative diseases, such as Alzheimer’s or Parkinson’s.

    To better understand this mechanism, the researchers used a machine-learning approach they developed in 2016 to figure out exactly how the proteins break up one mitrochondrion into two smaller ones. They also used a powerful technique called “synchrotron small-angle X-ray scattering” at the Stanford Synchrotron Radiation Lightsource, a U.S. Department of Energy research facility, to see how these proteins deform mitochondrial membranes during this process.

    SLAC/SSRL

    Before this study, it was thought that these proteins encircled the mitochondria, then cut it in two by simply squeezing tightly. The process, the team discovered, is more subtle.

    “When Dnm1 wraps around mitochondria, it has been previously shown that the protein physically tightens and pinches,” said Michelle Lee, a recent UCLA bioengineering doctoral graduate who was advised by Wong and is one of two lead authors of the study. “What we found is that when Dnm1 contacts the mitochondrial surface, it also makes that area of the mitochondrion itself more moldable and easier to undergo cleavage. These two effects work hand in hand to make the process of mitochondrial division efficient.”

    The other lead author is Ernest Lee, a graduate student in the UCLA-Caltech Medical Scientist Training Program and a bioengineering graduate student also advised by Wong. He carried out the computational analyses for the experiment.

    “Using our machine-learning tool, we were able to discover hidden membrane-remodeling activity in Dnm1, consistent with our X-ray studies,” Lee said. “Interestingly, by analyzing distant relatives of Dnm1, we found that the protein gradually evolved this ability over time.”

    “This is a very unexpected result — no one thought these molecules would have a split personality, with both personalities necessary for the biological function,” said Wong, who is also a UCLA professor of chemistry and biochemistry and is a member of the California NanoSystems Institute. “The multifunctional behavior we identified may be the rule rather than the exception for proteins.”

    Other authors include Andy Ferguson from the University of Illinois at Urbana-Champaign and Blake Hill from the Medical College of Wisconsin.

    The research was supported by the National Science Foundation and the National Institutes of Health, with additional support from the Department of Energy for imaging experiments.

    See the full article here .

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    For nearly 100 years, UCLA has been a pioneer, persevering through impossibility, turning the futile into the attainable.

    We doubt the critics, reject the status quo and see opportunity in dissatisfaction. Our campus, faculty and students are driven by optimism. It is not naïve; it is essential. And it has fueled every accomplishment, allowing us to redefine what’s possible, time after time.

    This can-do perspective has brought us 12 Nobel Prizes, 12 Rhodes Scholarships, more NCAA titles than any university and more Olympic medals than most nations. Our faculty and alumni helped create the Internet and pioneered reverse osmosis. And more than 100 companies have been created based on technology developed at UCLA.

     
  • richardmitnick 8:03 am on September 1, 2017 Permalink | Reply
    Tags: , , Nanocrystals rapidly forming superlattices while they are themselves still growing, , , Scientists Watch ‘Artificial Atoms’ Assemble into Perfect Lattices with Many Uses, SLAC Stanford SSRL, Superlattices can form superfast   

    From SLAC: “Scientists Watch ‘Artificial Atoms’ Assemble into Perfect Lattices with Many Uses” 


    SLAC Lab

    July 31, 2017
    Andrew Gordon
    agordon@slac.stanford.edu
    (650) 926-2282
    Written by Glennda Chui

    1
    An illustration shows nanocrystals assembling into an ordered ‘superlattice’ – a process that a SLAC/Stanford team was able to observe in real time with X-rays from the Stanford Synchrotron Radiation Lightsource (SSRL). They discovered that this assembly takes just a few seconds when carried out in hot solutions. The results open the door for rapid self-assembly of nanocrystal building blocks into complex structures with applications in optoelectronics, solar cells, catalysis and magnetic materials. (Greg Stewart/SLAC National Accelerator Laboratory)

    A serendipitous discovery lets researchers spy on this self-assembly process for the first time with SLAC’s X-ray synchrotron. What they learn will help them fine-tune precision materials for electronics, catalysis and more.

    Some of the world’s tiniest crystals are known as “artificial atoms” because they can organize themselves into structures that look like molecules, including “superlattices” that are potential building blocks for novel materials.

    Now scientists from the Department of Energy’s SLAC National Accelerator Laboratory and Stanford University have made the first observation of these nanocrystals rapidly forming superlattices while they are themselves still growing. What they learn will help scientists fine-tune the assembly process and adapt it to make new types of materials for things like magnetic storage, solar cells, optoelectronics and catalysts that speed chemical reactions.

    The key to making it work was the serendipitous discovery that superlattices can form superfast – in seconds rather than the usual hours or days – during the routine synthesis of nanocrystals. The scientists used a powerful beam of X-rays at SLAC’s Stanford Synchrotron Radiation Lightsource (SSRL) to observe the growth of nanocrystals and the rapid formation of superlattices in real time.

    SLAC/SSRL

    A paper describing the research, which was done in collaboration with scientists at the DOE’s Argonne National Laboratory, was published today in Nature.

    “The idea is to see if we can get an independent understanding of how these superlattices grow so we can make them more uniform and control their properties,” said Chris Tassone, a staff scientist at SSRL who led the study with Matteo Cargnello, assistant professor of chemical engineering at Stanford.

    Tiny Crystals with Outsized Properties

    2
    Stanford Assistant Professor Matteo Cargnello at a lab in the Stanford Chemical Engineering Department where nanocrystals are grown. Cargnello and Chris Tassone, a staff scientist at SLAC’s Stanford Synchrotron Radiation Lightsource (SSRL), led a team that discovered how superlattices can grow unexpectedly fast – in seconds, rather than hours or days – during routine nanocrystal synthesis. (Dawn Harmer/SLAC National Accelerator Laboratory)

    Scientists have been making nanocrystals in the lab since the 1980s. Because of their tiny size –they’re billionths of a meter wide and contain just 100 to 10,000 atoms apiece — they are governed by the laws of quantum mechanics, and this gives them interesting properties that can be changed by varying their size, shape and composition. For instance, spherical nanocrystals known as quantum dots, which are made of semiconducting materials, glow in colors that depend on their size; they are used in biological imaging and most recently in high-definition TV displays.

    In the early 1990s, researchers started using nanocrystals to build superlattices, which have the ordered structure of regular crystals, but with small particles in place of individual atoms. These, too, are expected to have unusual properties that are more than the sum of their parts.

    But until now, superlattices have been grown slowly at low temperatures, sometimes in a matter of days.

    That changed in February 2016, when Stanford postdoctoral researcher Liheng Wu serendipitously discovered that the process can occur much faster than scientists had thought.

    3
    The experimental set-up at SLAC’s Stanford Synchrotron Radiation Lightsource (SSRL) where scientists used an X-ray beam to observe superlattices forming during the synthesis of nanocrystals for the first time. The vessel where the reactions took place is at bottom center, wrapped in gold heating tape that boosted the temperature inside to more than 230 degrees Celsius. (Liheng Wu/Stanford University)

    ‘Something Weird Is Happening’

    He was trying to make nanocrystals of palladium – a silvery metal that’s used to promote chemical reactions in catalytic converters and many industrial processes – by heating a solution containing palladium atoms to more than 230 degrees Celsius. The goal was to understand how these tiny particles form, so their size and other properties could be more easily adjusted.

    The team added small windows to a reaction chamber about the size of a tangerine so they could shine an SSRL X-ray beam through it and watch what was happening in real time.

    “It’s kind of like cooking,” Cargnello explained. “The reaction chamber is like a pan. We add a solvent, which is like the frying oil; the main ingredients for the nanocrystals, such as palladium; and condiments, which in this case are surfactant compounds that tune the reaction conditions so you can control the size and composition of the particles. Once you add everything to the pan, you heat it up and fry your stuff.”

    Wu and Stanford graduate student Joshua Willis expected to see the characteristic pattern made by X-rays scattering off the tiny particles. They saw a completely different pattern instead.

    “So something weird is happening,” they texted their adviser.

    The something weird was that the palladium nanocrystals were assembling into superlattices.

    A Balance of Forces

    At this point, “The challenge was to understand what brings the particles together and attracts them to each other but not too strongly, so they have room to wiggle around and settle into an ordered position,” said Jian Qin, an assistant professor of chemical engineering at Stanford who performed theoretical calculations to better understand the self-assembly process.

    Once the nanocrystals form, what seems to be happening is that they acquire a sort of hairy coating of surfactant molecules. The nanocrystals glom together, attracted by weak forces between their cores, and then a finely tuned balance of attractive and repulsive forces between the dangling surfactant molecules holds them in just the right configuration for the superlattice to grow.

    To the scientists’ surprise, the individual nanocrystals then kept on growing, along with the superlattices, until all the chemical ingredients in the solution were used up, and this unexpected added growth made the material swell. The researchers said they think this occurs in a wide range of nanocrystal systems, but had never been seen because there was no way to observe it in real time before the team’s experiments at SSRL.

    “Once we understood this system, we realized this process may be more general than we initially thought,” Wu said. “We have demonstrated that it’s not only limited to metals, but it can also be extended to semiconducting materials and very likely to a much larger set of materials.”

    The team has been doing follow-up experiments to find out more about how the superlattices grow and how they can tweak the size, composition and properties of the finished product.

    Ian Salmon McKay, a graduate student in chemical engineering at Stanford, and Benjamin T. Diroll, a postdoctoral researcher at Argonne National Laboratory’s Center for Nanoscale Materials (CNM), also contributed to the work.

    SSRL and CNM are DOE Office of Science User Facilities. The research was funded by the DOE Office of Science and by a Laboratory Directed Research and Development grant from SLAC.

    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.
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  • richardmitnick 9:23 pm on April 11, 2017 Permalink | Reply
    Tags: , , , , , , SLAC Stanford SSRL, Theory Institute for Materials and Energy Spectroscopies (TIMES), ,   

    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 .

    Please help promote STEM in your local schools.

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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.
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