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       SEMINAR OF THE LABORATORY FOR COMPUTER DESIGN OF MATERIALS
        Institute for Computational Sciences and Informatics
		CSI 929  (http://science.gmu.edu/physics/)
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           Generalized density functionals for bandstructure calculations

                                 Gerhard E. Engel
Institute for Computational Sciences and Informatics, George Mason University
				    and
  Complex Systems Theory Branch, Naval Research Laboratory, Washington D. C.

  Traditional density functionals for electronic systems, such as the local 
density approximation (LDA) and generalized gradient approximations (GGA), are 
not very well suited for the description of excitation energies in solids. Band 
gaps, for example, are systematically underestimated. It is widely believed that
this failure is inherent to density functional theory, because it is a ground 
state theory which is not designed to describe excited states. In this talk,
I show that it is nonetheless possible to construct density functionals which 
not only accurately describe ground state properties, but whose eigenvalue
spectra are much closer to the true excited state spectra than those calculated
within LDA or GGA. This is achieved by deviating from the usual Kohn-Sham 
partitioning of the density functional.

  We discuss several possible functionals, with particular emphasis on
a recently developed 'local mass approximation', which greatly improves
the description of free-electron like metals and which also yields
improved bandgaps in a number of semiconductors. I also present some general 
results for hybrid functionals which interpolate between Hartree-Fock and 
density functional theory.

	               Monday , September 30 1996
                                 5:00 pm
                        Room 206, Science & Tech. I
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