Ab-Initio-Based Atomistic Potentials and Application to Metallic Surface and Interface Structures

Abstract

In this paper we present a new ab initio technique for developing atomistic potentials designed for dynamic study of transition metal intermetallics and alloys; and we give an illustrative application of that technique to the behavior of NiAℓ. The fact that crystals exhibit plasticity shows the importance of modeling potentials which give a correct energetic description of materials under large deformation. We will show that total energy calculations within density functional theory (DFT) provide a flexible way to develop potentials with wide applicability. Starting from a simple mathematical transformation between atomic volume and a local variable function, developing these potentials relies on density functional theory (DFT) total energy calculations. The potential parameters in the model are determined by fitting energy surfaces resulting from total energy calculations within DFT on crystals at zero temperature. We have already successfully applied this model to study thermal properties of nickel-rich alloys^1,2. Here, after discussing the development of the potential, we discuss the calculation of some surface and interface properties of NiAℓ using this model potential to check its quality. Excellent results are obtained compared with both DFT ab initio calculations and experiment. We then present results of molecular dynamics (MD) simulation of tensile deformation performed on unalloyed NiAℓ crystals with and without a simple defect structure (simulated grain boundary). Details of the atomic motion have been followed and will be illustrated in the case of plastic deformation.