First principles calculations in V–Si system. Defects in A15-V3Si phase

The structural and thermodynamic properties of vanadium silicides have been obtained from DFT calculations. The calculated values of the enthalpies of formation and of the lattice parameters at T = 0 K agree well with the experimental values. We have studied the defects in the A15-V3Si compound and found that the dominant defects are antisites. Using a simple statistical model, the atomic defects concentrations and the corresponding thermodynamic data have been obtained. The enthalpies of mixing of V and Si on the two sublattices of the A15 structure have been obtained from total energy of A15 supercells. In order to describe the equilibrium between the A15 phase and the A2 solid solution based on vanadium, calculations of the enthalpy of mixing of the A2 solid solution have been performed by using supercells and special quasi random structures. The V-rich part of the V–Si phase diagram has been calculated using the data obtained from ab intio total energy calculations.