Development of an interatomic potential for titanium with high predictive accuracy of thermal properties up to melting point

摘要

In this paper, we present an interatomic potential predicting thermal properties of phases of titanium in their temperature range of stability at zero pressure. The potential was developed within the approach proposed by A.G. Lipnitskii and V.N. Saveliev for atomic systems with metallic and covalent types of bonds, which exactly describes three-particle interactions. The parameters of the potential were optimized to the database of results of density-functional calculations and known experimental data for hexagonal close-packed phase of Ti. The developed potential correctly describe omega-Ti as the ground state at zero temperature. Prediction of the point-defect energies, stacking fault energies, surface energies, specific heat, and thermal expansion is in reasonable agreement with the experimental and density-functional data. This indicates the transferability of the potential to describe phases of titanium in a wide range of temperatures. Melting point of beta-Ti predicted using the developed potential is in excellent agreement with the experimental value. For the developed potential the lowest temperature of the mechanical stability of the beta phase equals to 1156 K, at which the spontaneous transition to the a phase occurs. The volume of the transformation from beta to alpha phase is correctly predicted by the developed potential in agreement with the experimental value. MD simulations in combination with Gibbs-Helmholtz integration show that the alpha phase is mechanically and thermodynamically stable at any temperature up to melting temperature of the beta-Ti. The constructed potential can be applied for modeling the beta phase at its range of mechanical stability as well as alpha phase at temperatures up to melting point of the beta-Ti.