Abstract
The optical and electronic properties of fluoro-perovskites XYF3 (X = K, Ag, Rb; Y=Zn, Sr, Mg) were investigated under pressure ranging from 0 to 50 GPa, utilizing full potential method based on density functional theory (DFT). The generalized gradient approximation GGA-PBE and GGA-PBEsol functional are used for calculating the structural properties while TB-mBJ functional is employed for the calculation of optical and electronic properties. The lattice constant increases by varying the cation from Zn to Mg to Sr. The volume-ratios as a function of pressure reveal that AgZnF3 has a low compressibility among the whole series of these compounds. At zero pressure, all these compounds exhibit indirect wide bandgap. The band gap of AgMgF3, KMgF3, KZnF3, RbMgF3 and RbZnF3 increases with pressure, while that of AgZnF3 and KSrF3 first increases with rising the pressure from zero to 10 Gpa for AgZnF3 and from zero to 5 Gpa for KSrF3 and then, decreases smoothly with increasing the pressure up to 50 GPa. The band gap type of RbSrF3 and KSrF3 change from indirect to direct at a pressure of 5 GPa and 40 Gpa, respectively. The high pressure shows significant influence on the density of states; it reduces and shift the highest peaks towards negative energy with broader bandwidths. The electron density plots explored a mixed covalent as well as ionic bonding at zero pressure. The covalent bonding becomes stronger under high pressure. The optical conductivity, refractive index and reflectivity spectra reveal a blue shift with the rise in pressure, due to rise in the band gap and the broadening of bands with compression.