High Pressure Study of New Type of MAX Phases: Hf2AB2 (A = In, Sn)

This study carries out density functional theory (DFT)-based simulation in order to observe the effect of pressure (up to 120 GPa) on the various physical properties of boron (B) containing new MAX compounds Hf2InB2 and Hf2SnB2. Structural parameters in ambient conditions show excellent concordance with prior experimental and theoretical data. A decreasing trend of lattice parameters with pressure is observed. The stability of the phases under pressure is determined by calculating the elastic constant using the Born stability criteria, and is found stable within the studied pressure range. Pressure's effect on the various elastic moduli is considered, and a linear response with pressure is observed. The brittle/ductile behavior under pressure is investigated, and a brittle to ductile phase transition is found. An opposite trend of elastic moduli with pressure is observed for Vickers hardness. The nonlinear variation of Vickers hardness with pressure has been interpreted in terms of Pugh ratio and density of states (DOS). A decreasing trend of the anisotropic indices is observed for Hf2InB2, while an increasing trend is observed for Hf2SnB2. The electronic and optical properties are also significantly influenced by the pressure. The results obtained at zero GPa have been compared with previous results and show significant agreement.