X-ray absorption spectroscopy studies of local structure and electronic properties of NaxSi136 (0 < x < 24) clathrates.
Date
2010
Authors
Ritchie, Andrew D.
MacDonald, Mark A.
Zhang, Peng
White, Mary Anne
Beekman, Matt
Gryko, Jan
Nolas, George S.
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Abstract
The local structure and electronic properties were probed of Na-contg. type II Si clathrates by
x-ray absorption spectroscopy. The near-edge region of the spectrum is particularly sensitive to the
local structure surrounding the Na atom. Through exptl. studies of 8 samples NaxSi136, with x
ranging from ∼0 to 21.5, and simulation of extended x-ray absorption fine structure (EXAFS) and
x-ray absorption near-edge structure spectra (XANES), Na is primarily in the larger Si28 cages at
low loadings, and loss of the Na relative to full cage occupancy occurs preferentially from the
smaller Si20 cages. The EXAFS results also show that Na is dynamically disordered in the Si28 cages
but less disordered at higher Na loadings. Local-orbital d. of states calcns. indicate that the Na
in the Si20 cage has a charge of 0.7e- while Na in the Si28 cages has a slightly higher
(loading-dependent) charge (0.72e- to 0.8e-).
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Citation
Ritchie, Andrew D., Mark A. MacDonald, Peng Zhang, Mary Anne White, et al. 2010. "X-ray absorption spectroscopy studies of local structure and electronic properties of NaxSi136
(0 < x < 24) clathrates.." Physical Review B: Condensed Matter and Materials Physics 82(15): 1552071-155207/9. Copyright © 2010 American Physical Society.