NMR experiments and electronic structure calculations in type-I BaAlGe clathrates Academic Article uri icon

abstract

  • We describe A 27 l NMR experiments on Ba8 Alx Ge46-x type-I clathrates coupled with ab initio computational studies. For x=16, calculated spectra determined by the ab initio results gave good agreement with the measurements, with best-fitting configurations also corresponding to the computed lowest-energy atomic arrangements. Analysis of the NMR results showed that a distribution of Knight shifts dominates the central portion of the line. Computational results demonstrate that this stems from the large variation of carrier density on different sites. Al-deficient samples with x=12 and 13 exhibited a split central NMR peak, signaling two main local environments for Al ions, which we connected to the presence of vacancies. Modeling of the wide-line spectrum for x=12 indicates a configuration with more Al on the 24k site than for x=16. The results indicate the importance of nonbonding hybrids adjacent to the vacancies in the electronic structure near EF. We also address the static distortions from Pm 3 n symmetry in these structures. 2009 The American Physical Society.

published proceedings

  • Physical Review B

author list (cited authors)

  • Gou, W., Rodriguez, S. Y., Li, Y., & Ross, J. H

publication date

  • January 1, 2009 11:11 AM