Detailed interpretation of the 5f-6d absorption spectrum of U3+ in Cs2NaYCl6 and high pressure effects based on an ab initio simulation

The 5f -> 6d(t(2g)) absorption spectrum of U3+-doped Cs2NaYCl6 is simulated with a quantum chemical ab initio embedded-cluster approach applied to U3+ substitutional defects of O-h local symmetry. The first-principles results help to provide a detailed interpretation of the very rich experimental absorption spectrum of this material between 14 000 and 25 000 cm(-1). Also, the effects of high pressures up to 26 kbars on the absorption spectrum are predicted, the most relevant feature being a redshift of around 21 cm(-1)/kbar, which is the fingerprint of a bond length shortening upon 5f -> 6d(t(2g)) excitation. (C) 2007 American Institute of Physics.