Vibrational properties and superconductivity in

¹ Department of Physics and Engineering Physics, University of Saskatchewan Saskatoon, S7N 5E2 Canada
² Computational Astrophysics Laboratory, RIKEN - 2-1 Hirosawa Wako, Saitama, 351-0198, Japan
³ Institute of Nuclear Physics, Polish Academy of Sciences ul. Radzikowskiego 152, 31-342 Cracow, Poland

Received: 20 March 2006
Accepted: 10 May 2006

Abstract

The vibrational spectrum for the type-III Si-clathrate has been computed from first principles electronic structure method. It is shown that the vibrations are strongly hybridized with the host lattice in the cages formed by coordinately unsaturated Si. The electron-phonon coupling spectral function calculated from zone center phonons indicates that electron-phonon interaction is stronger for low-frequency vibrations in the loosely enclathrated cages than those in the more tightly fitted cages. A similar trend was also observed in the related and systems. The results show that low-frequency rattling vibrations of the atoms are very efficient in mediating electron-phonon coupling in the superconductivity behaviour of these novel materials.