Phonon density of states and the vibronic spectra of impurities in K2PtCl6-type single crystals

Single crystals of the K2PtCl6 type at 4°K with impurities of Re+4, Os+4, and Ir+4 show optical absorption with extended phonon structure. To understand the details of this, a phonon density of states was calculated using the model of O'Leary and Wheeler for K2ReCl6 and the method of Gilat and Raubenheimer. The results are compared with the optical spectra of Re+4 and Os+4 in K2PtCl6 that provide strong evidence that the previously used k = 0 phonon analysis is incorrect and that all the lattice vibrations must be used. The implications in the calculation of phonon assisted transition selection rules are discussed.