Pressure-induced phase transitions and structural properties of CoF2: An ab-initio molecular dynamics study

The crystal structure of CoF2 was studied theoretically using first-principles density functional theory (DFT) methods within the generalized gradient approximation (GGA) and local density approximation (LDA) under rapid hydrostatic pressure up to 144 GPa. CoF2 undergoes a structural phase transformation from the rutile-type tetragonal parent phase with space group P42/mnm to the CaCl2-type orthorhombic parent phase with space group Pnnm at 64 GPa with GGA and at 96 GPa with LDA methods. Another phase transformation occurs from the CaCl2-type structure to monoclinic parent phase with space group P21/c at 96 GPa with a GGA method. These phase transitions are also studied by enthalpy and total energy calculations. According to these calculations, we obtained the first phase transformation at about 6.5 GPa both GGA and LDA methods and the later phase transformation at about 45 GPa with the GGA method.