Discover New Materials for Batteries Through Modeling

March 12th, 2010 by Admin

In the 21st century, materials and energy are more topical than ever before. Insights at the atomistic and quantum level help us to design cleaner energy sources, and find less wasteful ways of using energy. Join us on March 16th as Dr. George Fitzgerald presents “High-throughput Quantum Chemistry and Virtual Screening for Lithium Ion Battery Electrolyte Materials.”

Register to learn:

  • How modeling can support the discovery of components to enhance the performance of lithium ion battery formulations
  • How to use Materials Studio components in Pipeline Pilot to analyze and screen a materials structure library for Li-Ion battery additives
  • Results from a collaboration with Mitsubishi Chemical Inc which was also published in The Journal of Power Sources

This presentation is part of our ongoing webinar series that showcases how Accelrys products and services are transforming materials research. You can download related archived presentations in this series or register for future webinars.

We look forward to sharing our insights with you throughout this webinar series.

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Spectroscopy: Where Theory Meets the Real World

February 23rd, 2010 by George Fitzgerald, PhD

One of the most successful uses of quantum mechanical modeling methods is to predict spectra. These methods are capable of yielding good predictions of UV/Visible, NMR, Infrared, Raman, THz, and EELS (electron energy loss spectroscopy) to name just a few. Spectroscopy (according to Wikipedia) is the “study of the interaction between radiation and matter as a function of wavelength … or frequency.” How does this help chemists? We can use the spectra to determine the structure of new molecules or materials; to determine the composition of mixtures; or to follow the course of a chemical reaction in situ. How does modeling help with this? In a number of ways, but I’ll cover just 2.

One way modeling comes into play is by working with experimental results to remove ambiguities. When a chemist is trying the determine the structure of a new material, he or she takes a spectrum, or two, or three. His or her knowledge of the ingredients together with the spectra gives a pretty good idea what the chemical or crystal structure is. In a lot of cases the data are sufficient only  to narrow this down to 3-4 possible structures. Molecular modeling resolve this ambiguity by predicting the spectrum of each possibility; the spectrum that matches the experimental one presumably corresponds to the “right” one. Modeling is even more valuable when investigating defect structures like this work on Mg2.5VMoO8.

Another use is telling where experimentalists to look for the spectral peaks of a new compound. This can be especially important when trying to detect the spectra of new, novel, or poorly characterized materials. Experimental terahertz (THz) spectroscopy, for example, examines the spectral range of 3-120 cm-1, and can be used for detection and identification for a wide assortment of compounds including explosives like HMX. It’s a lot safer to investigate these materials by modeling than in the lab.

A recent blog by Dr. Damian Allishighlights the importance of doing the simulations correctly. (By the way, Damian, congrats on getting to page 1000.) A lot of work for the past 40-odd years has gone into predicting spectra of isolated – or gas phase – molecules. But materials like HMX are crystalline, and calculations on the isolated molecules make for poor comparison with crystals. The recent work underscores how important it is to simulate crystals using crystals. And it’s not just for THz spectra. Recent work on NMR leads to the same conclusion. A couple of programs can do this. Damian’s blog focuses on DMol3 and Crystal06, but we should also mention CASTEP and Gaussian as other applications capable of predicting a wide variety of properties for solids.

Let’s keep modeling – but be careful out there: short cuts will lead to poor results, and molecular modeling will end up taking the rap for user error.

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Materials and Energy: A Maturing Relationship

February 11th, 2010 by Gerhard Goldbeck-Wood, PhD

After simple combustion, and the nuclear option, the relationship between materials and energy is as topical as ever. Taking a new turn in the 21st century the couple have matured into exploring more subtle ways to relate to each other. What am I talking about? Well, there are so many ways in which materials affect energy and energy is affected by materials, i.e. energy generation, storage, conservation and the efficient use of energy. In all of these, insights at the atomistic and quantum level help us to design cleaner energy sources, and find less wasteful ways of using energy. To find out more on how modelling supports the discovery and understanding of new materials for fuel cells and batteries, please check out the Materials Studio 5.0 Webinar Series.  Following the recent webinar on fuel cell catalysts (for which you can still access the recording), we have two more webinars scheduled on the topic:

February 17th, 2pm GMT/6am PST: Atomic-Scale Insights into Materials for Clean Energy. The webinar will be given by Prof Saiful Islam from University of Bath, who is a renowned expert in the field: check out the interviews, podcasts and publications.

March 16th, 3pm GMT/8am PDT:  High-throughput Quantum Chemistry and Virtual Screening for Lithium Ion Battery Electrolyte Materials . George Fitzgerald will include results from a collaboration with Mitsubishi Chemical Inc which was also published in The Journal of Power Sources.

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Theory and Experiment in “Step” on Semiconductors

February 8th, 2010 by George Fitzgerald, PhD

A recent news article by the University of Texas at Dallas (UTD)  highlighted recent joint work by the Department of Materials Science and Engineering and Accelrys on critical surface reactions of Silicon. The research points the way to ”improve semiconductor devices’ performance in health care and solar power applications in particular.”

Who cares? Anybody who uses chips, solar cells, or any other device containing semiconductors (in other words, all of us.)  

Insertion of Nitrogen atom is predicted to occur preferentially at the step edge of Si(111)

 How does the latest research help? A typical semiconductor device consists of a metal oxide semiconductor layer (e.g., HfO2) deposited on a silicon substrate. As explained by co-author Dr. Mat Halls, formation of an SiO2interlayer between the silicon substrate and metal oxide can decrease semiconductor performance. One approach to solving this is to introduce a nitride barrier to prevent the growth of interfacial SiO2. The ability to introduce such heteroatoms into the topmost layers of Si affords additional opportunities to tune the surface properties by enhancing chemical reactivity at these sites to form functional surfaces. But how do you get the nitrogen to stick to the surface?     

In the latest research, published in Nature Materials, used infra-red spectroscopy  to explore the possible formation mechanisms of nitride on silicon surfaces terminated by hydrogen. Calculations using density functional theory (DFT) demonstrated how stepped edges are important to formation of the nitride layers. The reaction mechanism on the stepped surface provides a means of controlling the reaction. As the authors wrote: “The ability to control the reaction … enables the realization of applications … including sensing, electrical and thermal transport, and molecular computing.” This is a beautiful demonstration of the complementarity of theory and experiment. One can deal with facts, but requires interpretation. The other provides detailed explanations at the atomic level, but sometime requires an anchor to the “real world.” Together they can do more. Wouldn’t it be great if all viewpoints could be reconciled this well?

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Theory Meets Industry In Nagoya

November 12th, 2009 by George Fitzgerald, PhD

I’ve enjoyed 2 days so far in Nagoya attending the “Theory Meets Industry” conference. There is some amazing work going on by both developers of computational methods and those who apply them. We’ve heard from developers like Bernard Delley and his recent work onTDDFT in DMol3, which will enable excited state calculations and UV spectra. We’ve also heard from Georg Kresse about his recent work on the Random Phase Approximation (RPA),which offers a way to improve not just DFT band gaps but total energies, as well.

There’s been an emphasis in alternative energy from the industrial participants. Applications are really diverse:

  • Rradiation damage in reactor containment materials by Christophe Domain of EDF
  • Improved solar cells by Royji Asahi of Toyota Central R&D Labs
  • Fischer-Tropsch catalysis by Werner Janse van Rensburg of Sasol Technologies
  • Hydrogen storage materials by Pascal Raybaud of IFP

This list also reflects the true international spirit of the conference.

I’ve also heard some interesting new approaches to doing calculations fast while not sacrificing accuracy. Gabor Csanyi of Cambridge University presented his Gaussian Approximation Potentials (GAP), an alternative to force fields that spans more of the potential energy surface. And Isao Tanaka of Kyoto University showed how he uses an improved Cluster Expansion method to study phase transitions. Keep your eye on these methods for future developments.

Today I make my own small contribution by presenting my work on high-throughput computation. Look for details on that in a future blog.

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DFT Goes (Even More) Mainstream

October 25th, 2009 by George Fitzgerald, PhD

When I did my graduate work in quantum chemistry, doing a calculation on something the size of, say, hexatriene was a huge deal. In those days, the calculations were limited to people with expertise and perseverance – and a lot of patience. GUI? We didn’t need no stinkin’ GUI. We set up input files by hand, even had to work out the Cartesian coordinates of the atoms on a hand calculator. Those times have changed.

A combination of factors helped to make quantum mechanical calculations accessible to a wider range of users:

  • Computers got faster. These calculations take a long time, but computers today are around 1,000-10,000x faster than when I was in grad school.
  • Modeling methods got faster. Besides simply optimizing software performance, there were breakthrough approaches like density functional theory (DFT), which delivered reliable results with less CPU time.
  • Graphical User Interfaces (GUIs). Yes, it turns out that we do need those stinkin’ GUIs. It’s just not feasible to set up calculations for anything more than around a dozen atoms without a sketcher.

DFT has done particularly well over the past 10 years or so. On top of everything else, the methods have been extended to include systems with periodic boundary conditions, so chemists have started getting into solid state calculations. With this approach you can study heterogeneous catalysis on an extended (periodic) surface; predict crystal structures; or calculate elastic constants. Searching ACS Number of occurrences of 'Density Functional Theory' in ACS journals has grown by about 25% each year since 1990for “density functional theory” shows a staggering increase from 37 publications in1989 to almost 4000 so far this year.

Among some interesting research directions are those to compute solid-state spectra. This includes NMR, Raman, and EELS (electron energy loss spectra), all of which are part of the drive to make DFT more relevant by connecting theory with experiment. Raman is used, for example, to characterize reactions in situ. NMR can be used to discriminate among crystal polymorphs. EELS has “enabled detailed measurements of the atomic and electronic properties of single columns of atoms, and in a few cases, of single atoms.” Earlier this year, there was even a workshop sponsored by the Oxford University Department of Materials to promote these computational approaches specifically to the experimental community. This combination of theory and experiment facilitates the identification of unknown compounds; the elucidation of reaction mechanisms; and the characterization of molecular & crystal structure.

One of the most gratifying measures of success is the appearance of articles not directed at other specialists. NewScientist recently ran an article about using DFT to predict crystal structure entirely from first principle – a sort of DFT for the common man type article.

As a developer and practitioner of DFT, I’m really pleased to see how far the awareness of theory in general and DFT in particular has spread. Who knows: someday there may even be an iPhone application for DFT.

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Political Catalysis

September 29th, 2009 by Michael Doyle, PhD

Just reading a recent Financial Times and I noticed on the front page that the German Chancellor Agela Merkel, and her husband Joachim Sauer, the ex director of the historical Catalyst Consortium from part of Accelrys, were sharing what I guess was a scientific joke. It is interesting that through the initial part of Chancellor Merkel’s election campaign Joachim Sauer kept a very low profile, declining to give any interviews not related to his scientific work, but has recently been seen more in public with his wife. Joachim, a Professor of Quantum Chemistry and a historical collaborator with Accelrys, has a strong technical background in advanced catalyst modeling and its further interesting that in Germany where arguably the modern chemical catalysis industry began, now at the highest levels of government there is a voice for advanced virtual chemical screening and analysis. I hope that this is the sign of an increased acceptance and interest in the virtual chemical and quantum space area in all levels of government.

Photo from the Financial Times of Joachim Sauer and his wife, German Chancellor Agela Merkel

Photo from the Financial Times of Joachim Sauer and his wife, German Chancellor Agela Merkel

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