First-principles study on structural, electronic, and elastic properties of SrFCl

Structural, electronic, and elastic properties of SrFCl, one of the alkaline-earth fluorohalides, under high pressure were investigated using the Siesta Package Program within the framework of density functional theory. SrFCl crystallizes in a tetragonal matlockite type structure belonging to the space group P-4/nmm at ambient conditions. The phase transformation from a tetragonal matlockite type structure to an orthorhombic type structure belonging to the space group Pmmn occurred in the presence of gradually increasing simulation pressure. The values of lattice parameters, shear modulus, Young's modulus, and bulk modulus, for the obtained structures of SrFCl were investigated. The transition pressure value was calculated by total energy and enthalpy calculations. The electronic properties of SrFCl were also calculated. Band gaps of 6.52 eV for the P-4/nmm phase and 3.55 eV for the Pmmn phase were obtained. Thus, it was concluded that the P-4/nmm and Pmmn phases of SrFCl have an insulator and a semiconductor character, respectively. In addition to these studies, the mechanical stability of SrFCl was investigated by calculating elastic constants. As a result of this calculation, both phases of SrFCl were mechanically stable.