NMR Knight shifts and the electronic properties of Rb{sub 8}Na{sub 16}Si{sub 136} clathrate
A silicon framework clathrate type-II compound was synthesized with rubidium and sodium atoms in cages. A single crystal of this material was characterized by both conventional and synchrotron x-ray diffraction; the structure belongs to the cubic space group Fd-3m, with a cell edge of 14.738(1) Aa. The alkali metals are ordered in the structure, with the small cages containing sodium, and the large cages containing rubidium. Variable temperature magic-angle-spinning NMR of all three nuclei show large Knight shifts with a strong temperature dependence, unlike conventional metals. The low conductivity (200 S/cm) and high paramagnetic susceptibility (5x10{sup -6}emu/g) indicate that as the temperature is lowered, the electrons become more localized on the alkali atoms, resulting in properties consistent with a correlated narrow band metal system.
- Sponsoring Organization:
- (US)
- OSTI ID:
- 40205450
- Journal Information:
- Physical Review B, Journal Name: Physical Review B Journal Issue: 12 Vol. 63; ISSN 0163-1829
- Publisher:
- The American Physical Society
- Country of Publication:
- United States
- Language:
- English
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