- Monte Carlo atomistic simulations of the properties of Σ3111 grain boundaries in W are carried out. We demonstrate the influence of boron additive on the resistance of the grain boundary with respect to different shifts. The interatomic potentials used in these simulations are obtained from ab initio total-energy calculations. These calculations are performed in the framework of density functional theory in the coherent potential approximation. A recursion procedure for extracting A-B-type interatomic potentials is suggested.