Analysis of the local structure around Cr~(3+) centers in perovskite KMgF_3 using both ab initio (DFT) and semi-empirical (SPM) calculations

摘要

The local structure around Cr~(3+) centers in perovskite KMgF_3 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+)-VMg and Cr~(3+)-Li+), trigonal (Cr~(3+)-VK), and CrF_5O 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_3.