A shell model for cross relaxation in elpasolite crystals: application to the 3P0 and 1G4 states of Cs2NaY1−xPrxCl6

A model for cross relaxation in high symmetry systems is developed. The positions of all acceptor ions and all multipole-multipole interactions may be included. The geometric factors are explicitly considered. A feature of the model is that it enables decay rates and the form of decay curves to be predicted a priori if the exponential decay curves of very dilute and stoichiometric materials are experimentally accessible. The model is applied to the title system and excellent agreement with experiment is achieved.