ABINITIO MODEL POTENTIAL STUDY OF PRESSURE EFFECTS ON K2NAGAF6-CR3+

In this paper we present the results of an ab initio study of the pressure effects on the 4A2g ground state and the 4T2g and 2E(g) excited states of Cr3+-doped K2NaGaF6. Complete active space SCF (CASSCF) and averaged coupled-pair functional (ACPF) calculations are performed on a CrF63- cluster embedded in an ab initio model potential (AIMP) representation of the K2NaGaF6 lattice at ambient and high pressure. The results are in close agreement with the experimentally measured pressure shifts of vibrational frequencies and emission spectra, which demonstrates the ability of the ab initio embedding model potential method to accurately model hydrostatic pressure experiments in this type of defect crystals. It is also shown that if only the standard Madelung embedding potential is used, none of the observed effects of pressure are reproduced.