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           COLLOQUIUM OF THE COMPUTATIONAL MATERIALS SCIENCE CENTER
                              College of Science
                       (CDS Department CSI 898-Sec 001)
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                    The electronic structure of cathode materials: 
                           How to build a better battery

                                 Michelle Johannes

                     Center for Computational Materials Science
                       Naval Research Laboratory, Washington DC

From cell phones to laptops to music players, Li ion batteries are almost 
everywhere in the technology we use.  The constant push for smaller, lighter 
and longer lasting devices necessitates that better and more efficient 
materials be found for battery components, particularly cathodes. Density 
functional theory can be used to predict several of the important electrochemical 
properties of a potential cathode material. Therefore, the search for a better 
battery can be done computationally, saving both time and money in the 
laboratory. DFT also makes it possible to study the relationship between the 
physical structure of a cathode and its performance properties at the electronic 
structure level and to isolate the underlying mechanisms that control the voltage, 
conductivity, and capacity, and stability of a material
                         
In this talk, I will explain the basic physics and chemistry behind Li ion batteries 
and show how DFT can be used to predict which materials are suitable as cathodes.  As 
an example of how the electronic structure of a material determines its properties, 
I will compare two cathode materials that have identical chemical constituents and the 
same local structure, but are radically different in terms of battery performance.The 
differences can be explained in terms of their respective energy levels, and general 
lessons about choosing a cathode material can be extracted from an understanding of their 
electronic structures.
                        Monday , September 24, 2007
                                  4:30 pm
                     Room 301, Research I, Fairfax Campus

Refreshments will be served at 4:15 PM.
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Find the schedule at www.cmasc.gmu.edu/seminar/schedule.html
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