Comparison of the atomic level structure of the plastic crystalline and the liquid phases of CBr2Cl2: neutron diffraction and Reverse Monte Carlo modeling

TL;DR

This study compares the atomic structures of plastic crystalline and liquid phases of CBr2Cl2 using neutron diffraction and Reverse Monte Carlo modeling, highlighting the dominance of steric effects over dipole interactions.

Contribution

It provides a detailed atomic-level comparison of the crystalline and liquid phases of CBr2Cl2, emphasizing the role of steric effects in molecular orientation.

Findings

Neighbouring molecule orientation is mainly influenced by steric effects.

Dipole moment has limited impact on short-range order.

Results align with previous studies on related compounds.

Abstract

Neutron diffraction results obtained for plastic crystalline dichlorodibromomethane (CBr2Cl2) have been modelled by means of the Reverse Monte Carlo method. Comparison with its liquid phase is provided at several levels of the atomic structure (total scattering structure factors, partial radial distribution functions, orientational and dipole-dipole correlations). Results reveal that the relative orientation of neighbouring molecules largely depends on the steric effect. The small dipole moment has not as strong influence as the steric effect on the short range order. Our observations fit well with earlier findings presented for the series CBrnCl4-n (n=0, 1, 2, 4).