COMPUTER MODELING OF THERMAL QUENCHING OF CHROMIUM PHOTOLUMINESCENCE IN FLUORIDE ELPASOLITES

Radiationless transition rates were predicted ab initio in K2NaScF6:Cr 3+ and K2NaGaF6:Cr3+. Embedded cluster calculations provided adiabatic potential energy functions of a1g, e(g) and t2g nearest-neighbor fluo rine displacements in both ground (4A2g) and excited (4T2g) states. Tr ansition rates were calculated from normalized lineshape functions G ( OMEGA) derived by evaluating vibrational overlap integrals for an arbi trary combination of linear, quadratic and anharmonic coupling. Predic ted transition rates, which are lower than experimental values, were n ot improved by including anharmonicity.