The N-body interatomic potential for molecular dynamics simulations of diffusion in tungsten

Tungsten, as the most refractory metal, is applied in fusion reactor in parts subjected to high temperatures and strong neutron irradiation. These factors lead to intense diffusion processes causing degradation of the material. Experimental investigations under such conditions are usually highly complicated and cannot provide a comprehensive understanding of the occurring phenomena. Therefore, their combination with theoretical approaches is required. One of the most robust approaches to simulate diffusion processes is molecular dynamics simulations based on classical interatomic potentials. It allows modeling relatively large samples consisting of several grains, grain boundaries, dislocations, and other types of defects for a reasonable computational time. The reliable simulations of the diffusion process require interatomic potentials satisfying the following criteria: prediction of melting point and thermal expansion as close as possible to the experimental values because the diffusion coefficient strongly depends on the homologous temperature and size factor. In the present paper, we present the new interatomic potential for tungsten, developed within the N-body approach, which reproduces the experimental value of melting temperature (3695 K) and thermal expansion at temperatures up to a melting point. The calculated diffusion coefficient demonstrates adequate agreement with experimental results. The constructed potential is applicable for simulation of processes involving diffusion, one of which is the irradiation damage.