Model calculation of vibronic sidebands in Cs2UBr6

A simple seven parameter lattice dynamics model for Cs2UBr6, employing a Urey−Bradley valence force field for the short range interactions and standard long range Coulomb terms, was used to calculate the shape of vibronic side bands accompanying a Γ1g → Γ1g and a Γ1g → Γ2g electronic transition. Simplifying assumptions concerning the vibronic interaction were made. The results were fairly good and instructuve for the sideband accompanying the Γ2g electronic transition partly because the vibronic effective Hamiltonian was more realistic in that case.