Europhys. Lett.
Volume 75, Number 1, July 2006
Page(s) 153 - 159
Section Condensed matter: electronic structure, electrical, magnetic, and optical properties
Published online 07 June 2006
Europhys. Lett., 75 (1), pp. 153-159 (2006)
DOI: 10.1209/epl/i2006-10078-8

Vibrational properties and superconductivity in $\chem{Ba_{24}Si_{100}}$

J. S. Tse1, T. Iitaka2 and K. Parlinski3

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 in final form 10 May 2006
published online 7 June 2006

The vibrational spectrum for the type-III Si-clathrate $\chem{Ba_{24}Si_{100}}$ has been computed from first principles electronic structure method. It is shown that the $\chem{Ba}$ 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 $\chem{Ba}$ vibrations in the loosely enclathrated cages than those in the more tightly fitted cages. A similar trend was also observed in the related $\chem{Ba_{8}Si_{46}}$ and $\chem{Ba_{6}Na_{2}Si_{46}}$ systems. The results show that low-frequency rattling vibrations of the $\chem{Ba}$ atoms are very efficient in mediating electron-phonon coupling in the superconductivity behaviour of these novel materials.

74.25.Kc - Phonons.
74.25.Fy - Transport properties (electric and thermal conductivity, thermoelectric effects, etc.).
74.10.+v - Occurrence, potential candidates.

© EDP Sciences 2006