Electronic structure and vibrational properties of Ba8Si46-n, Ba8AgnSi46-n, and Ba8AunSi46-n -: art. no. 155441

The electronic and vibrational structures of Ba8Si46 and Ba8MnSi46-n, where some of the framework Si were replaced by metal (M=Ag or Au) have been studied. Theoretical calculations show that the nature of chemical bonding of the substituted clathrates and their vibrational properties are fundamentally different from Ba8Si46. Low-frequency vibrations associated with the motions of Ba in the large cages and the framework metals have been identified from their Raman spectra. A surprisingly large contribution of the low-frequency modes, particularly those which arise from the Ba vibrations in the large cages, to the electron-phonon coupling parameter in Ba8Si46 was found.