Crystal structure, bonding, and phase transition of the superconducting Na[sub 2]CsC[sub 60] fulleride
- Univ. of Sussex, Brighton (United Kingdom)
- NEC Corporation, Tsukuba (Japan)
The crystal structure of superconducting Na[sub 2]CsC[sub 60] was studied by high-resolution powder neutron diffraction between 1.6 and 524 K. Contrary to the literature, the structure at low temperatures is primitive cubic (Pa3), isostructural with pristine C[sub 60]. Anticlockwise rotation of the C[sub 60] units by 98[degrees] about [111] allows simultaneous optimization of C[sub 60]-C[sub 60] and alkalifulleride interactions. Optimal Na[sup +]-C[sub 60][sup 3[minus]] coordination is achieved with each sodium ion located above one hexagon face and three hexagon-hexagon fusions of neighboring fulleride ions (coordination number 12). Reduction of the C[sub 60] molecule lengthens the hexagon-hexagon fusions and shortens the pentagon-hexagon fusions (to [approximately]1.43 angstroms). On heating, Na[sub 2]CsC[sub 60] undergoes a phase transition to a face-centered-cubic Fm3m phase, best modeled as containing quasi-spherical C[sub 60][sup 3[minus]] ions. The modified structure and intermolecular potential provide an additional dimension to the behavior of superconducting fullerides and should sensitively affect their electronic and conducting properties.
- OSTI ID:
- 7103231
- Journal Information:
- Science (Washington, D.C.); (United States), Journal Name: Science (Washington, D.C.); (United States) Vol. 263:5149; ISSN SCIEAS; ISSN 0036-8075
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
360602* -- Other Materials-- Structure & Phase Studies
360606 -- Other Materials-- Physical Properties-- (1992-)
ALKALI METAL COMPOUNDS
CARBON
CESIUM COMPOUNDS
CHEMICAL BONDS
CRYSTAL STRUCTURE
ELEMENTS
FULLERENES
NONMETALS
ORGANIC SUPERCONDUCTORS
PHASE TRANSFORMATIONS
SODIUM COMPOUNDS
SUPERCONDUCTORS