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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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      Tight-binding Methodologies for Efficient Electronic Structure
                 and Total Energy Calculations

                  Dimitrios A. Papaconstantopoulos
            Center for Computational Materials Science, 
             Naval Research Laboratory,Washington DC and
 School of COmputational Sciences, George Mason University, Fairfax, VA

Quantum mechanically accurate first-principles calculations for real
materials are computationally limited to no more than 100-500
atoms depending on the method used. Atomistic potentials methods can
handle much larger systems but their results are often limited to just
reproducing the database to which they are fitted.
Tight-binding (TB) methods operate between these two extremes.
In the TB methods the quantum mechanical behavior of the
electrons is maintained, but the computational effort is much less
than needed for first-principles calculations of comparable size.
This talk describes the NRL Tight-Binding Method (NRL-TB), which
maps the results of a limited set of first-principles calculations
to a two-center non-orthogonal Slater-Koster TB Hamiltonian.  The
on-site Hamiltonian parameters are sensitive to the local environment 
and the hopping parameters are bond-length dependent.

  The method has been shown to successfully determine elastic constants, 
phonon frequencies, vacancy formation energies,and surface energies. In 
addition,TB molecular dynamics simulations are used to study mean square 
displacements and thermal expansion. We will discuss applications to 
spin-polarized systems, and multi-component systems, such as the newly 
discovered superconductor MgB2, semiconductor compounds (SiC), 
transition-metal carbides and aluminides, and ferroelectric materials 
such as PbZrO3. I will also present a revision of Harrison's TB theory 
which transforms this excellent qualitative description of the 
electronic structure to a more quantitative basis.

                         Monday , November 3, 2003
                                  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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