Structural,elastic, electronic and optical properties of platinum-based superconductor SrPt3P under pressure: a first-principles study

The structural, elastic, electronic and optical properties of the platinum-based superconductor SrPt₃P under pressure are investigated by the generalized gradient approximation with the Perdew–Burke–Ernzerhof exchange-correlation functional in the framework of density-functional theory. The calculated structural parameters (a, c) and the primitive cell volume V of SrPt₃P at the ground state are in good agreement with the available experimental data and seem to be better than other calculated results. The pressure dependences of the elastic constants \mathop C\nolimits_{ij}, bulk modulus B, shear modulus G, Young’s modulus E and Poisson’s ratio σ of SrPt₃P are also obtained successfully. The computed elastic constants indicate that SrPt₃P is mechanically stable up to 100 GPa. The obtained B/G is 2.56 at the ground state, indicating that SrPt₃P behaves in a ductile manner. The ratio B/G also increases with growing pressures, indicating that the structure becomes more and more ductile. Even though SrPt₃P is an ionic-covalent crystal, the obtained density of states shows that it has metallic characteristic. These conclusions can be further demonstrated by analysing the charge and Mulliken population. In addition, we have investigated the dielectric function and the loss function. It is found that the dielectric function in (E||x, E||y) is isotropic, whereas the directions (E||x, E||z) are anisotropic; the effect of pressure on the loss function of the deep ultraviolet region gradually increases as the pressure increases.