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  • richardmitnick 10:13 am on January 8, 2019 Permalink | Reply
    Tags: , , , Infrared spectroscopy, , , , X-ray spectroscopy   

    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 .


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  • richardmitnick 1:50 pm on November 7, 2018 Permalink | Reply
    Tags: , , , , , , , Researchers create most complete high-res atomic movie of photosynthesis to date, , , X-ray spectroscopy   

    From SLAC National Accelerator Lab: “Researchers create most complete high-res atomic movie of photosynthesis to date” 

    From SLAC National Accelerator Lab

    November 7, 2018

    Andrew Gordon
    agordon@slac.stanford.edu
    (650) 926-2282

    In a major step forward, SLAC’s X-ray laser captures all four stable states of the process that produces the oxygen we breathe, as well as fleeting steps in between. The work opens doors to understanding the past and creating a greener future.

    1
    Using SLAC’s X-ray laser, researchers have captured the most complete high-res atomic movie to date of Photosystem II, a key protein complex in plants, algae and cyanobacteria responsible for splitting water and producing the oxygen we breathe. (Gregory Stewart, SLAC National Accelerator Laboratory)

    Despite its role in shaping life as we know it, many aspects of photosynthesis remain a mystery. An international collaboration between scientists at SLAC National Accelerator Laboratory, Lawrence Berkeley National Laboratory and several other institutions is working to change that. The researchers used SLAC’s Linac Coherent Light Source (LCLS) X-ray laser to capture the most complete and highest-resolution picture to date of Photosystem II, a key protein complex in plants, algae and cyanobacteria responsible for splitting water and producing the oxygen we breathe. The results were published in Nature today.

    SLAC/LCLS

    Explosion of life

    When Earth formed about 4.5 billion years ago, the planet’s landscape was almost nothing like what it is today. Junko Yano, one of the authors of the study and a senior scientist at Berkeley Lab, describes it as “hellish.” Meteors sizzled through a carbon dioxide-rich atmosphere and volcanoes flooded the surface with magmatic seas.

    Over the next 2.5 billion years, water vapor accumulating in the air started to rain down and form oceans where the very first life appeared in the form of single-celled organisms. But it wasn’t until one of those specks of life mutated and developed the ability to harness light from the sun and turn it into energy, releasing oxygen molecules from water in the process, that Earth started to evolve into the planet it is today. This process, oxygenic photosynthesis, is considered one of nature’s crown jewels and has remained relatively unchanged in the more than 2 billion years since it emerged.

    “This one reaction made us as we are, as the world. Molecule by molecule, the planet was slowly enriched until, about 540 million years ago, it exploded with life,” said co-author Uwe Bergmann, a distinguished staff scientist at SLAC. “When it comes to questions about where we come from, this is one of the biggest.”

    A greener future

    Photosystem II is the workhorse responsible for using sunlight to break water down into its atomic components, unlocking hydrogen and oxygen. Until recently, it had only been possible to measure pieces of this process at extremely low temperatures. In a previous paper, the researchers used a new method to observe two steps of this water-splitting cycle [Nature]at the temperature at which it occurs in nature.

    Now the team has imaged all four intermediate states of the process at natural temperature and the finest level of detail yet. They also captured, for the first time, transitional moments between two of the states, giving them a sequence of six images of the process.

    The goal of the project, said co-author Jan Kern, a scientist at Berkeley Lab, is to piece together an atomic movie using many frames from the entire process, including the elusive transient state at the end that bonds oxygen atoms from two water molecules to produce oxygen molecules.

    “Studying this system gives us an opportunity to see how metals and proteins work together and how light controls such kinds of reactions,” said Vittal Yachandra, one of the authors of the study and a senior scientist at Berkeley Lab who has been working on Photosystem II for more than 35 years. “In addition to opening a window on the past, a better understanding of Photosystem II could unlock the door to a greener future, providing us with inspiration for artificial photosynthetic systems that produce clean and renewable energy from sunlight and water.”

    Sample assembly line

    For their experiments, the researchers grow what Kern described as a “thick green slush” of cyanobacteria — the very same ancient organisms that first developed the ability to photosynthesize — in a large vat that is constantly illuminated. They then harvest the cells for their samples.

    At LCLS, the samples are zapped with ultrafast pulses of X-rays [Science] to collect both X-ray crystallography and spectroscopy data to map how electrons flow in the oxygen-evolving complex of photosystem II. In crystallography, researchers use the way a crystal sample scatters X-rays to map its structure; in spectroscopy, they excite the atoms in a material to uncover information about its chemistry. This approach, combined with a new assembly-line sample transportation system [Nature Methods], allowed the researchers to narrow down the proposed mechanisms put forward by the research community over the years.

    Mapping the process

    Previously, the researchers were able to determine the room-temperature structure of two of the states at a resolution of 2.25 angstroms; one angstrom is about the diameter of a hydrogen atom. This allowed them to see the position of the heavy metal atoms, but left some questions about the exact positions of the lighter atoms, like oxygen. In this paper, they were able to improve the resolution even further, to 2 angstroms, which enabled them to start seeing the position of lighter atoms more clearly, as well as draw a more detailed map of the chemical structure of the metal catalytic center in the complex where water is split.

    This center, called the oxygen-evolving complex, is a cluster of four manganese atoms and one calcium atom bridged with oxygen atoms. It cycles through the four stable oxidation states, S0-S3, when exposed to sunlight. On a baseball field, S0 would be the start of the game when a player on home base is ready to go to bat. S1-S3 would be players on first, second, and third. Every time a batter connects with a ball, or the complex absorbs a photon of sunlight, the player on the field advances one base. When the fourth ball is hit, the player slides into home, scoring a run or, in the case of Photosystem II, releasing breathable oxygen.

    The researchers were able to snap action shots of how the structure of the complex transformed at every base, which would not have been possible without their technique. A second set of data allowed them to map the exact position of the system in each image, confirming that they had in fact imaged the states they were aiming for.

    1
    In photosystem II, the water-splitting center cycles through four stable states, S0-S3. On a baseball field, S0 would be the start of the game when a batter on home base is ready to hit. S1-S3 would be players waiting on first, second, and third. The center gets bumped up to the next state every time it absorbs a photon of sunlight, just like how a player on the field advances one base every time a batter connects with a ball. When the fourth ball is hit, the player slides into home, scoring a run or, in the case of Photosystem II, releasing the oxygen we breathe. (Gregory Stewart/SLAC National Accelerator Laboratory)

    Sliding into home

    But there are many other things going on throughout this process, as well as moments between states when the player is making a break for the next base, that are a bit harder to catch. One of the most significant aspects of this paper, Yano said, is that they were able to image two moments in between S2 and S3. In upcoming experiments, the researchers hope to use the same technique to image more of these in-between states, including the mad dash for home — the transient state, or S4, where two atoms of oxygen bond together — providing information about the chemistry of the reaction that is vital to mimicking this process in artificial systems.

    “The entire cycle takes nearly two milliseconds to complete,” Kern said. “Our dream is to capture 50-microsecond steps throughout the full cycle, each of them with the highest resolution possible, to create this atomic movie of the entire process.”

    Although they still have a way to go, the researchers said that these results provide a path forward, both in unveiling the mysteries of how photosynthesis works and in offering a blueprint for artificial sources of renewable energy.

    “It’s been a learning process,” said SLAC scientist and co-author Roberto Alonso-Mori. “Over the last seven years we’ve worked with our collaborators to reinvent key aspects of our techniques. We’ve been slowly chipping away at this question and these results are a big step forward.”

    In addition to SLAC and Berkeley Lab, the collaboration includes researchers from Umeå University, Uppsala University, Humboldt University of Berlin, the University of California, Berkeley, the University of California, San Francisco and the Diamond Light Source.

    Key components of this work were carried out at SLAC’s Stanford Synchrotron Radiation Lightsource (SSRL), Berkeley Lab’s Advanced Light Source (ALS) and Argonne National Laboratory’s Advanced Photon Source (APS). LCLS, SSRL, APS, and ALS are DOE Office of Science user facilities. This work was supported by the DOE Office of Science and the National Institutes of Health, among other funding agencies.

    SLAC/SSRL

    LBNL/ALS

    ANL APS

    See the full article here .


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  • richardmitnick 9:46 am on April 25, 2018 Permalink | Reply
    Tags: A SLAC Legend Gives the Lab His Lifetime Collection of Precious Foils, , , Calibration foils including several extremely rare elements, , Farrel Lytle, , , X-ray Science, X-ray spectroscopy   

    From SLAC Lab: “A SLAC Legend Gives the Lab His Lifetime Collection of Precious Foils” 


    SLAC Lab

    1
    Farrel Lytle’s career-long collection of calibration foils, including several extremely rare elements, is now available to SLAC users at SSRL. (Courtesy of Farrel Lytle)

    April 23, 2018
    Bobbi Fagone

    The foils, each made from a single chemical element, are used to calibrate X-ray equipment at SLAC’s SSRL synchrotron, and were donated by long-time user, Farrel Lytle.

    SLAC/SSRL

    Scientists who conduct experiments at the Stanford Radiation Synchrotron Lightsource (SSRL) have received an unusual and highly valuable gift—a library of element calibration foils for a technique used to understand the structure of matter called X-ray absorption spectroscopy.

    SSRL, a DOE Office of Science user facility at the SLAC National Accelerator Laboratory, offers scientists extremely bright X-ray beams to probe samples at the atomic and molecular level. X-ray absorption spectroscopy is used in a variety of studies, including physics, materials science, chemistry (such as the study of catalysts used to promote and control many chemical reactions), earth science and biology.

    The foils were donated by entrepreneur, scientist and X-ray spectroscopy pioneer, Farrel W. Lytle, and include precious metals such as gold, silver, platinum, iridium and many other elements in the periodic table.

    “The machines on the beam lines at SSRL are not always absolutely correct,” Lytle explains. “They may vary a little bit. So, scientists can use these pure elements to do a measurement, and then adjust their instrumentation so it’s exactly right.”

    Each foil is a tiny strip of metal one-fifth of the thickness of a postage stamp, similar to a piece of cellophane. “You can get some of these elements in bulk, but not thin like this,” says Lytle. This is vital because the X-rays need to penetrate the element to complete the measurement. Over the years, Farrel made many of the foils himself or had them created by a machinist. But the entire collection, valued at $10,000, took a lifetime to build.

    “I measured my first X-ray edge on a synchrotron in 1974 at SSRL,” Lytle recalls. “But I had been working on this problem in my own lab with my own equipment since 1960. Because whenever you change the experiment, you change the chemistry and you need new reference compounds.

    “This collection of thin metal foils may not look like much, but it represents all of the different elements that I worked on during my career,” he continues. “Some of those most difficult to obtain are of interest for current projects at SSRL. While many elements are easily available as pure, thin foils (such as copper, silver and gold) many others are hard, brittle, rare and not available commercially. So, these elements would have to be created using difficult and/or expensive techniques.”

    Fortunately, the foils are not consumed in the experiments when used as reference samples, so they can be used over and over again. Lytle describes the process as “just like shining a light on them.” The measured X-ray spectrum (a fingerprint-type of X-ray picture) of the pure metal is used to calibrate the experimental apparatus, and also to observe the changes to the atomic and electronic environment of the same type of element when exposed to the conditions of the experiment.

    An SSRL Trailblazer Gives Back

    A long-time visiting user of SSRL, Lytle is a well-known SLAC personality. Formerly a Boeing researcher, Lytle’s experiments at SSRL in the 1970s furthered the science of X-ray spectroscopy. He also authored and co-authored early papers describing the synchrotron X-ray technique and its first applications.

    In 1998, the first Farrel W. Lytle Award was presented to him at an annual conference and bears his name to this day. This annual award recognizes important technical or scientific accomplishments in synchrotron radiation-based science and collaboration between visiting scientists and staff at SSRL.

    “Every time I went to SSRL, I thought, ‘How wonderful that I get to work on this thing. All I have to do is have an idea, get it approved and it’s free,’” says Lytle. “I owe them! Donating these foils was a chance for me to give back.”

    At 83, Lytle continues to work as the sole proprietor of a business he founded in 1974. He’s also busy building a special kind of X-ray detector that is used specifically in synchrotron experiments. “At the moment I have more business than I can handle,” he says. “Right now, I’m building three of these things.”

    How about retiring? Maybe just go play golf? “I don’t play golf,” Lytle laughs. “It just ruins a good walk.”

    3
    Farrel and Manetta Lytle at their beloved desert home in Eagle Valley, Lincoln County, Nevada. (Courtesy of Farrel Lytle)

    See the full article here .

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  • richardmitnick 8:22 am on June 23, 2017 Permalink | Reply
    Tags: , , , How a Single Chemical Bond Balances Cells Between Life and Death, Protein cytochrome c, , , X-ray spectroscopy,   

    From SLAC: “How a Single Chemical Bond Balances Cells Between Life and Death” 


    SLAC Lab

    June 22, 2017
    Amanda Solliday

    1
    An optical laser (green) excites the iron-containing active site of the protein cytochrome c, and then an X-ray laser (white) probes the iron a few femtoseconds to picoseconds later. The critical iron-sulfur bond is broken as the optical laser heats the protein, and rebinds as the system cools. (Greg Stewart/SLAC National Accelerator Laboratory)

    Slight changes in the machinery of a cell determine whether it lives or begins a natural process known as programmed cell death. In many forms of life—from bacteria to humans—a single chemical bond in a protein called cytochrome c can make this call. As long as the bond is intact, the protein transfers electrons needed to produce energy through respiration. When the bond breaks, the protein switches gear and triggers the breakdown of mitochondria, the structures that power the cell’s activities.

    For the first time, scientists have measured exactly how much energy cytochrome c puts into maintaining that bond in a state where it’s strong enough to endure, but easy enough to break when the cell’s life span is ending.

    They used intense X-rays from two facilities, the Linac Coherent Light Source (LCLS) X-ray free-electron laser and the Stanford Synchrotron Radiation Lightsource (SSRL) at the Department of Energy’s SLAC National Accelerator Laboratory.

    SLAC/LCLS

    SLAC/SSRL

    The collaboration, led by Edward Solomon, professor of chemistry at Stanford University and of photon science at SLAC, published their results today in Science.

    “This is a very general yet extremely important process in biochemistry, and with an X-ray laser we now have insight into how this regulation works,” says Roberto Alonso-Mori, LCLS staff scientist and a co-author of the study. “These are processes that are going on a million-fold in our bodies and everywhere there is life.”

    The study marks the first time that anyone has been able to experimentally quantify how the rigid structure of the cytochrome c molecule supports this crucial bond between iron and sulfur atoms in what’s known as an entatic state, where the protein maintains a bond that is just strong enough to perform both of its jobs, says Michael Mara, lead author of the study and a former postdoctoral researcher at Stanford University, now at University of California, Berkeley.

    “This was important because we had shown the bond is weak and shouldn’t be present at room temperature in the absence of the protein constraints,” says Solomon. “But the protein is able to contribute energy to keep this bond intact for electron transfer. In this LCLS experiment, we determined exactly how much energy the rest of the protein contributes to maintaining the bond: about 4 kcal/mol that is derived from an adjacent hydrogen bond network.”

    “We were able to show how nature tunes this system to change the properties on a fundamental level and perform two very different functions,” Mara says. “The energy contribution by cytochrome c is really at a sweet spot. It makes me wonder what sort of similar effects you might see in other protein systems, and it makes us realize that there is exciting new science on the horizon.”

    Ultrafast Changes

    Cytochrome c is present in a wide range of life forms and contributes to both cellular respiration and programmed cell death, the pathway to the natural end of a cell’s life cycle. How exactly the state of the bond relates to these two functions had not yet been demonstrated or quantified.

    Scientists knew from earlier studies that a particular iron-sulfur bond is key. When iron in the protein binds to sulfur contained in one of the protein’s amino-acid building blocks, cytochrome c participates in electron transfer. By transferring electrons, the protein helps generate energy needed for biological processes that maintain life.

    But when cytochrome c encounters cardiolipin, a lipid present in the membrane of the cell’s mitochondria, the iron-sulfur bond breaks, and the protein becomes an enzyme that creates holes in the mitochondria’s outer membrane – the first step in programmed cell death.

    These changes occur incredibly fast, in less than 20 picoseconds, so the experiment required ultrafast pulses of X-rays generated by LCLS to take snapshots of the process.

    “We photoexcited the iron atoms in the protein’s active site—which contains an iron-rich compound known as heme—with an ultrafast laser before probing it with the LCLS X-ray pulses at different time delays,” says Alonso-Mori.

    Each 50-femtosecond laser pulse heated the heme by a couple of hundred degrees. X-ray pulses from LCLS took images of what happened as the heat traveled from the iron to other parts of the protein. After 100 femtoseconds, the iron-sulfur bond would break, only to form again once the sample cooled. Watching this process allowed the scientists to measure energy fluctuations in real time and better understand how this critical bond forms and breaks.

    “The entatic state concept is really interesting, but you have to come up with creative ways to demonstrate and quantify it,” says Ryan Hadt, a former Stanford University doctoral student on an Enrico Fermi Fellowship at Argonne National Laboratory who together with his advisor, Professor Solomon, came up with the idea for the experiment and co-wrote the initial proposal around the time LCLS first came online in 2009.

    “Our research group was excited about this new instrument and wanted to use it to do a definitive experiment,” Hadt adds.

    A Question Raised by Earlier Work

    This experiment builds on an earlier study [JACS] conducted at SSRL that found that the iron-sulfur bond was quite weak, says Thomas Kroll, staff scientist at SSRL and lead author of this prior study.

    In the latest study, spectroscopy at SSRL also built the framework for the LCLS pump-probe experiment. It allowed the scientists to compare what the molecule originally looked like to how it changed when the temperature rose.

    “It’s important to understand how these proteins actually work,” Kroll says. “Because if you don’t understand how they work, how can we create better medicines in an informed and controlled way?”

    Knowledge of cytochrome c’s function is also valuable to the fields of bioenergy and environmental science, since it is a critically important protein in bacteria and plants.

    The DOE Office of Science and the National Institute of General Medical Sciences of the National Institutes of Health supported this research. The Structural Molecular Biology program at SSRL is funded by DOE Office of Science and the National Institutes of Health, National Institute of General Medical Sciences. LCLS and SSRL are DOE Office of Science User Facilities.

    See the full article here .

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  • richardmitnick 9:23 pm on April 11, 2017 Permalink | Reply
    Tags: , , , , , , , Theory Institute for Materials and Energy Spectroscopies (TIMES), X-ray spectroscopy,   

    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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    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.
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