Coupled Oreintational and Displacive Degrees of Freedom in the High-Temperature Plastic Phase of the Carbon Tetrabromide alpha-CBr4
Two-dimensional single-crystal synchrotron x-ray diffraction of the high-temperature plastic phase of CBr4 reveals relatively sharp G{+-}1/2 {l_brace}110{r_brace}* sheets of diffuse intensity (where G represents the set of average structure Fm-3m allowed Bragg reflections). This intense and highly structured diffuse scattering arises from the large amplitude excitation of transverse polarized displacive modes of distortion and shows that a set of six possible orientations of the individual CBr4 molecules in the plastic phase are strongly coupled with displacive relaxational degrees of freedom. Using Monte Carlo simulations to model the diffuse intensity, the displacive relaxations are shown to be along the molecular nearest-neighbor 1/2{l_angle}110{r_angle} real space directions associated with the relative orientations of individual and nearest-neighbor CBr4 tetrahedra.
- Research Organization:
- Brookhaven National Lab. (BNL), Upton, NY (United States). National Synchrotron Light Source
- Sponsoring Organization:
- Doe - Office Of Science
- DOE Contract Number:
- DE-AC02-98CH10886
- OSTI ID:
- 960025
- Report Number(s):
- BNL-83011-2009-JA; PRBMDO; TRN: US1005881
- Journal Information:
- Physical Review B: Condensed Matter and Materials Physics, Vol. 77, Issue 14; ISSN 0163-1829
- Country of Publication:
- United States
- Language:
- English
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