Local order and orientational correlations in liquid and crystalline phases of carbon tetrabromide from neutron powder diffraction measurements
Abstract
The liquid, plastic crystalline and ordered crystalline phases of CBr4 were studied using neutron-powder diffraction. The measured total scattering differential cross sections were modeled by reverse Monte Carlo simulation techniques ( RMC++ and RMCPOW). Following successful simulations, the single-crystal-diffraction pattern of the plastic phase as well as partial radial distribution functions and orientational correlations for all the three phases have been calculated from the atomic coordinates (particle configurations). The single-crystal pattern, calculated from a configuration that had been obtained from modeling the powder pattern, shows identical behavior to the recent single-crystal data of Folmer [Phys. Rev. B 77, 144205 (2008)]. The BrBr partial radial-distribution functions of the liquid and plastic crystalline phases are almost the same while CC correlations clearly display long-range ordering in the latter phase. Orientational correlations also suggest strong similarities between liquid and plastic crystalline phases whereas the monoclinic phase behaves very differently. Orientations of the molecules are distinct in the ordered phase whereas in the plastic crystal their distribution seems to be isotropic.
- Publication:
-
Physical Review B
- Pub Date:
- April 2010
- DOI:
- 10.1103/PhysRevB.81.134101
- arXiv:
- arXiv:1003.2252
- Bibcode:
- 2010PhRvB..81m4101T
- Keywords:
-
- 61.43.Bn;
- 61.05.fm;
- 64.70.kt;
- Structural modeling: serial-addition models computer simulation;
- Neutron diffraction;
- Molecular crystals;
- Physics - Chemical Physics;
- Condensed Matter - Disordered Systems and Neural Networks;
- Condensed Matter - Materials Science
- E-Print:
- 19 pages, 7 figures, accepted for publication in Physical Review B (http://prb.aps.org/)