A comprehensive local structure analysis of Cr3+ centers in K2ZnF4 crystals: A semi-empirical approach

Abstract

Abstract The local structure around Cr3+ impurities forming four Cr3+ centers of different symmetries has been investigated by means of semi-empirical calculations in K<inf>2</inf>ZnF<inf>4</inf> crystal. Structural models for the all centers have been presented by analyzing their EPR data at various temperatures (297, 77, and 4.2 K). A similar trend is found that Cr3+-F- distances of the axial ligands decrease whereas those of the equatorial ligands increase when Zn2+ is replaced by Cr3+. It is indicated that the distortions around the orthorhombic centers are quite slight with respect to those of the tetragonal and monoclinic centers. We have also found that the displacements of the axial and equatorial ligands for the monoclinic center II and the orthorhombic center III change uniformly when the temperature decreases, while both axial and equatorial ligands for the tetragonal center I displace less from 293 to 77 K whereas more from 77 to 4.2 K. © 2019 Elsevier B.V., All rights reserved.