Lattice dynamics of AgBr

Abstract
A complete set of measured dispersion branches for the directions Delta ( xi 00), Sigma ( xi xi 0), Lambda ( xi xi xi ) and Z(1 xi 0) at 85K is presented. Special attention is paid to the L and W points. A model, which contains a quadrupole term for the Ag+ shell and a rotational term for the valence bond components on the Ag+, was fitted to the data. The quadrupolar and rotational terms, which take the influence of the 4d-electrons of the Ag+ into account, turned out to be very important. Derived quantities such as the density of states, the specific heat and the mean-square displacements are calculated from the fitted model.