A DFT STUDY OF STRUCTURAL, ELECTRONIC AND OPTICAL PROPERTIES OF KAF3 (A = MN, FE)

Abstract

It can be seen that this research deploys the density functional theory (DFT) and orthogonalized linear combination of atomic orbitals (OLCAO) method to carry out a systematic and comparative examination of the structure, electronic, and optical characteristics of cubic fluoro-perovskites KMnF3 and KFeF3. Both compounds are found to stabilize in their cubic perovskite structure (space group Pm-3m) characterized by lattice parameters of 4.18 A and 4.17 A, respectively, through geometry optimization. Both materials are found to have an electronic structure at the metallic ground state due to the lack of a band gap, and a finite density of states at the Fermi level. The main discovery is that KFeF3 has three bands crossing the Fermi level which is compared to only two in KMnF3 meaning that the charge carrier density is higher and the iron-based compound can conduct with a higher level of electricity. This is revealed through chemical bonding analysis, which shows that there is a high ionic character accompanied by strong covalent bonds between Mn-F and Fe-F which provides structural cohesion. Optical properties, the result of a complex dielectric-function, also support the conclusions of metallic behavior with a negative real part at low energies and sharp intra-band absorption peak at 0.0 eV. The optical conductivity of both compounds is large, and there are strong bulk plasmon peaks in the ultraviolet region as isoprominent in the electron energy loss function. These detailed observations explain the substitution behavior of transition metals on the basic properties of ABF3 perovskites, and their possible application in optoelectronic instruments and energy-related applications