Structure, elastic and thermodynamic properties of the Ni–P system from first-principles calculations

A systematic investigation concerned with the structure, elastic, and finite-temperature thermodynamic properties of Ni3P, Ni12P5, Ni2P, Ni5P4, NiP, cubic NiP2 (C- NiP2), monoclinic NiP2 (M- NiP2), and NiP3 in the Ni–P system is carried out via first-principles calculations. The elastic stiffness tensors and associated macroscopic elastic properties of these Ni–P compounds including the bulk modulus, shear modulus, Young’s modulus, and Poisson’s ratio are calculated. Within the framework of the quasi-harmonic approach, the finite-temperature thermodynamic properties of these Ni–P compounds including the Helmholtz free energy, entropy, heat capacity at constant pressure and enthalpy are predicted. The acquired thermodynamic properties are expected to be utilized for the thermodynamic modelling of the Ni–P system.

► The elastic stiffness tensors of Ni–P compounds are calculated with the stress–strain method. ► The four macroscopic elastic properties of the Ni–P compounds are calculated. ► The Helmholtz free energy, entropy, heat capacity and enthalpy at finite temperature are predicted.