In iron and many iron-based alloys the magnetic energy represents a significant contribution to the binding energy. An interatomic potential for the simulation of iron alloys therefore needs to include an adequate description of magnetism. In this talk I present the derivation of a magnetic interatomic potential that is suitable for simulating millions of atoms. The potential is obtained by systematically coarse graining the electronic structure from density functional theory through tight-binding to the bond-order potentials. I show that the resulting potential includes non-collinear magnetism and may be further simplified to a Ginzburg-Landau description of magnetism. Analytic expressions for forces and torques will be presented. Applications of the potential to modelling Fe, Fe-C and Mn will be discussed.
Ruhr-Universität Bochum Germany