Simulation of characteristics determining pressure effects on the concentration and diffusivity of vacancies in BCC metals: A new approach

Abstract

This work is devoted to the development of a new model (based on the molecular-statics method) for studying the diffusion properties of point defects in metals. In the model, a new algorithm is realized, which makes it possible in a self-consistent manner to calculate the atomic structure in the vicinity of a defect and the constants which determine atomic displacements in the elastic medium surrounding the computational cell. We also took into account the fact that the energy of the system depends on pressure. This dependence is different in the case of an ideal system and a system with a defect, which gives an additional contribution to the volumes of formation and migration. Furthermore, we took into consideration that the time required for an atom to jump into a vacancy is about that required for an atom to execute only a few vibrations in a lattice site. In this period, only atoms that are located in the immediate proximity to the center of dilation have time to respond for the disturbances arising in the system; therefore, when calculating the volume for the vacancy migration we carried out only a partial relaxation of the system. Within the framework of this model, we calculated the energies and volumes of vacancy formation and migration in different bcc metals.