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   COLLOQUIUM OF THE LABORATORY FOR COMPUTER DESIGN OF MATERIALS
                   School of Computational Sciences
                           (CSI 898-Sec 001)
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        Electronic Structure Calculations of Sodium Cobaltate

			   Michelle Johannes
                Center for Computational Materials Science 
               Naval Research Laboratory, Washington D. C.

        The family of sodium cobaltate compounds, Na_xCoO_2, is of wide
practical and theoretical interest.  A variety of doping levels, x, are
possible and give rise to a complex and still unresolved magnetic phase
diagram.  Its structure is identical to that of the lithium cobaltates,
already in common use for batteries, and the high thermopower at x=0.5
makes it a good candidate for solid state applications.  Recently, the
surprising discovery of superconductivity in the hydrated cobaltate was made,
stimulating a vast amount of experimental and theoretical work towards
understanding the origin of the superconducting transition.


        This talk will focus on the electronic structure of both the
superconducting and parent compounds.  First principles calculations
are used in conjunction with the tight-binding model to understand and
interpret, on a microscopic level, the behaviors that are observed 
experimentally. Because the bandstructure can be fit very accurately 
to a tight-binding Hamiltionian, the doping and structural dependencies 
of the fermi surface are computationally feasible.

                         Monday , April 5, 2004
                                  4:30 pm
                        Room 206, Science & Tech. I

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