Condensed Matter Seminar Series

Simulation of Materials Properties Using the Tight-Binding Method

Michael J. Mehl

Naval Research Laboratory

Thursday January 15,  11:00 am,  Room 298,  Physics Building

Abstract: Accurate first-principles quantum mechanical calculations for real materials are computationally limited to no more than 100-1000 atoms. At larger scales, atomistic potentials such as the Embedded Atom Method are used, but these methods may miss important physics driven by changes in the electronic structure, e.g., at cracks and defects. Parametrized tight-binding (TB) methods exist between these two extremes.  Unlike atomistic potentials, the quantum mechanical behavior of the electrons is maintained, but the computational effort is much less than needed for comparably sized first-principles calculations.  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 thermal expansion and atomic diffusion.  We will discuss applications to spin-polarized systems, non-collinear magnetization, and multi-component systems.  Possible improvements to the method will be discussed briefly.