NMR and computational study of Ba 8 Cu x Ge 46-x clathrate semiconductors

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Journal of Alloys and Compounds, ISSN: 0925-8388, Vol: 593, Page: 261-266

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http://scholars.library.tamu.edu/vivo/display/n127720SE; http://hdl.handle.net/1969.1/156030
Chen, Jing-Han; Sirusi Arvij, Ali; Zheng, Xiang; Rodriguez, Sergio Y.; Ross, Joseph H. Jr.
Elsevier BV; Elsevier
Engineering; Materials Science
article description
Ba 8 Cu x Ge 46-x is a type-I clathrate material that forms as a semiconductor in a narrow composition range corresponding to the electron-balanced Zintl composition, with x = 5.3. We use NMR spectroscopy combined with ab initio electronic structure calculations to probe the electronic and structural behavior of these materials. Computational results based on a superstructure model for the atomic configuration of the alloy provide good agreement with the electric quadrupole-broadened NMR lineshapes. Modeling using the modified Becke–Johnson (TB-mBJ) exchange potential is also shown to agree well with experimental NMR Knight shifts. The results indicate that the Cu–Ge balance is the main factor determining the carrier density, within a narrow stability range near the ideal Zintl composition.