Zhejiang Univ, Dept Mat Sci & Engn, Lab New Structed Mat, Hangzhou 310027, Peoples R China
; Chinese Acad Sci, Inst High Energy Phys, Beijing, Peoples R China
; Hangzhou Teacher Coll, Dept Phys, Hangzhou 310012, Peoples R China
; Tech Univ Denmark, Dept Chem, DK-2800 Lyngby, Denmark
; I Shou Univ, Dept Mech Engn, Kaohsiung, Taiwan
; Natl Sun Yat Sen Univ, Inst Mat Sci & Engn, Kaohsiung, Taiwan
Local structure of Cu in a type-I Ba8Cu4Si42 Clathrate has been investigated by synchrotron X-ray powder diffraction, Cu K-edge extended X-ray absorption fine spectroscopy, X-ray absorption near edge spectroscopy (XANES) and theoretical calculation. It is found that XANES spectra cannot be explained by the substitution of Cu atoms at Si16i, and Si24k positions. Our calculations show that the binding energies of the Si atom in Si16i, Si24k and Si6c positions are 9.000, 9.495 and 8.911 eV, respectively. Both experimental and theoretical results support that Cu atoms in the type-I Ba8Cu4Si42 clathrate, as a doped element, prefer to occupy the least-binding Si, i.e., the Si6c sites. No structural change between 112 and 300 K was observed and the (100)-faceted cubic crystal has negligible distortion/ordering according to transmission electron microscopy. (c) 2005 Elsevier Inc. All rights reserved.