New insight into the structural, elastic, dynamics and thermodynamic properties of Fe3P under high pressures

Many efforts have been devoted to developing the linkage between atomic characteristics and the mechanical properties. Equilibrium lattice parameters, elastic constants, dynamics and thermodynamic properties of Fe3P are systematically explored by density functional theory (DFT) calculations with a generalized gradient approximation (GGA) from Perdew-Wang's 1991 (GGA-PW91), Perdew-Burke- Erzenhof (GGA-PBE), local density approximation (LDA), GGA-PW91+U, GGA-PBE + U and (LDA) + U method (U is the Hubbard correction), respectively. It concluded that the lattice parameters and bulk modulus B from GGA-PBE + U results tend to be more compatible with experimental results than others. The elastic moduli of Fe3P is reported based on the VoigtReuss-Hill model. Meanwhile, the anisotropy index and the three dimensional (3D) surface profile of Young's modulus determine the anisotropy. The obtained results indicate that Fe3P exhibits strong elastic anisotropy under high pressure. In addition, the dynamical and mechanical stabilities of Fe3P are confirmed by calculating the phonon and elastic constants up to 40 GPa. Finally, we studied the thermodynamic properties of Fe3P under pressures based on quasi-harmonic approximation.