Bond-Order Potentials: From the electronic structure to million atom simulations

Ralf Drautz, Ruhr-Universität Bochum, Bochu, Germany

The analytic Bond-Order Potentials (BOPs) are derived from density functional theory (DFT) by two coarse-graining steps. In a first step the electronic structure is simplified to the tight-binding bond approximation by expanding the Hohenberg-Kohn-Sham energy functional to second order in charge and magnetic fluctuations. The second step achieves a local representation of the energy by rewriting the tight-binding approximation in a moments expansion. The BOPs encompass covalent bond formation, charge transfer and non-collinear magnetism within their derived functional form. The analytic BOP framework provides efficient and exact analytic forces and torques that enable simulations with millions of atoms. The BOP parameters follow in analogy by downfolding of the DFT wave functions on a optimized basis and interpolation of the resulting matrix elements.

In this talk I will outline the derivation of the BOPs, discuss their parameterization and give examples of the applications of the BOPs to modelling metals and steels.