Analysis of the local structure around Cr 3+ centers in perovskite KMgF 3 using both ab initio (DFT) and semi-empirical (SPM) calculations

Abstract

The local structure around Cr 3+ centers in perovskite KMgF <inf>3</inf> crystal have been investigated through the applications of both an ab-initio, density functional theory (DFT), and a semi empirical, superposition model (SPM), analyses. A supercell approach is used for DFT calculations. All the tetragonal (Cr 3+ -V <inf>Mg</inf> and Cr 3+ -Li + ), trigonal (Cr 3+ -V <inf>K</inf> ), and CrF <inf>5</inf> O cluster centers have been considered with various structural models based on the previously suggested experimental inferences. The significant structural changes around the Cr 3+ centers induced by Mg 2+ or K + vacancies and the Li substitution at those vacancy sites have been determined and discussed by means of charge distribution. This study provides insight on both the roles of Mg 2+ and K + vacancies and Li + ion in the local structural properties around Cr 3+ centers in KMgF <inf>3</inf> . © 2019 Elsevier B.V., All rights reserved.