Structure behavior and equation of state (EOS) of Ni2P and (Fe1 − x Nix)2P (allabogdanite) from First-principles calculations

First-principles calculations have been performed to determine the equations of state (EOS) and structural parameters of Ni2P, NiP2 (pyrite type) and Ni-doped Fe2P (allabogdanite) at high pressures. Ni2P (C22) is less compressible than hcp Fe, Fe2P (C22) and Fe2P (C23), because of its higher bulk modulus, found to be in good agreement with experimental results. Phase transition from C22 to C23 phase in Ni2P has not been observed up to 50 GPa. We have studied the structure parameters and the bulk modulus of (Fe1 − x Nix)2P (allabogdanite) in the concentration range (x = 0–0.187) of a stability region of allabogdanite phase. Bulk modulus of (Fe1 − x Nix)2P (allabogdanite) slightly increases with increase in doping concentration up to 18.75%. The resulting bulk modulus, however, is between Fe2P and Ni2P. Bulk modulus of Ni-doped Fe2P (C23) with maximum possible doping concentration is found to be larger than pure Fe2P (C23) by 7.6%.