Prediction of the diffusion characteristics of the V-Cr system by molecular dynamics based on N-body interatomic potentials

Abstract

Molecular dynamics (MD) is a promising method for predicting the diffusion characteristics of materials. However, the reliability of MD simulation results is largely determined by the technique of their interpretation and the interatomic potentials used. In this work, interatomic potentials are constructed for calculating the diffusion characteristics in alloys of the V-Cr system. We employed an approach that accurately takes into account the angular dependence of the potential energy of the atomic system. For monoatomic systems V and Cr, we used interatomic potentials that predict thermal expansion and melting point in good agreement with experimental values, along with good reproduction of BCC lattice parameters, sublimation energies, equations of state, elastic constants, and several other properties. The cross potential functions of the V-Cr binary system are optimized with using DFT calculations and experimental formation enthalpy values. The resulting V-Cr potential predicts the dependence of the BCC lattice parameter, the elastic constants of V-Cr solid solutions on the concentration of components and the thermal expansion of the stoichiometric V50Cr50 alloy in good agreement with the known experimental data. The constructed potentials were utilized to calculate the diffusion coefficients in V, Cr, V90Cr10 and V95Cr05 by the molecular dynamics method. We identified that the diffusion coefficient of V exceeds the diffusion coefficient of Cr in solid solutions of Cr in V. The calculated diffusion coefficients are consistent with the known results of diffusion experiments in V, Cr and Cr diffusion in V within the error of measurements. Inclusion of the temperature dependencies of the vacancy formation enthalpy and vacancy formation entropy into calculations of the diffusion coefficient leads to its deviation from the Arrhenius equation and improves the agreement with the experimental data.The good agreement between the independent results of the MD simulation and diffusion experiments confirms both the reliability of the experiment and the MD simulation.