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ID 30706
file
creator
Tanaka, Tomoo
Mano, Satomi
NDC
Physics
abstract
We report structural, transport, and thermal properties of type-I clathrate K8Ga8Sn38 single crystals grown by the self-flux method. Single-crystal x-ray diffraction analysis confirmed that the guest K+ ion locates on the center in the tetrakaidecahedron composed of Ga and Sn atoms. The thermopower is largely negative,-200μ V/K at room temperature, irrespective of the flux used during growth Ga or Sn . The thermal conductivity κ(T) exhibits a large peak at 14 K. These observations in K8Ga8Sn38 are ontrasting with the splitting of the guest site and the glasslike behavior in κ(T) reported for type-I Ba8Ga16Sn30 although the free space for the guest is almost the same in both compounds. The electrostatic potential for the tetrakaidecahedron was calculated using the occupation probabilities of Ga ions in the three sites on the cage. It is found that the off-centered state is stabilized for the Ba2+ ions in Ba8Ga16Sn30 by the partial occupation of Ga anion in the 16i site while the on-center state for K8Ga8Sn38 is stabilized by the strongly preferred occupation of Ga anions in the 6c site. We conclude that the charge distribution on the cage is crucial for the splitting of the guest site into off-center positions in the tetrakaidecahedron of the type-I clathrate.
journal title
Physical Review B
volume
Volume 81
issue
Issue 16
start page
165110-1
end page
165110-6
date of issued
2010
publisher
The American Physical Society
issn
1098-0121
ncid
publisher doi
language
eng
nii type
Journal Article
HU type
Journal Articles
DCMI type
text
format
application/pdf
text version
publisher
rights
Copyright (c) 2010 The American Physical Society
relation url
department
Graduate School of Advanced Sciences of Matter