Structure determination of liquid carbon tetrabromide via a combination of x-ray and neutron diffraction data and reverse Monte Carlo modeling

TL;DR

This study combines x-ray and neutron diffraction data with reverse Monte Carlo modeling to elucidate the atomic structure of liquid carbon tetrabromide, revealing subtle differences and providing a semi-quantitative reference model.

Contribution

It introduces a combined diffraction approach and analysis method to better understand the liquid structure of carbon tetrabromide, highlighting the limited additional information gained from extended Q-range.

Findings

Neutron and x-ray data yield similar structural insights.

Combined data suggest slightly higher order in C-C correlations.

A simple hard sphere model approximates the liquid's structure.

Abstract

In order to reveal the atomic level structure of liquid carbon tetrabromide, a new synchrotron x-ray diffraction measurement, over a wide momentum transfer (Q-)range, has been performed. These x-ray data have been interpreted together with a neutron diffraction dataset, measured earlier, using the reverse Monte Carlo method. The structure is analysed on the basis of partial radial distribution functions and distance dependent orientational correlation functions. Orientational correlations behave similarly to other carbon tetrahalides. Moreover, the information content of the new x-ray diffraction data set, and in particular, of the varying Q-range, is also discussed. Only very small differences have been found between results of calculations that apply one single experimental structure factor and the ones that use both x-ray and neutron diffraction data: the latter showed slightly more ordered carbon-carbon radial distribution function, which resulted in seemingly more ordered orientational correlations between pairs of molecules. Neither the extended Q-range, nor the application of local invariance constraints yielded significant new information. For providing a simple reference system, a hard sphere model has also been created that can describe most of the partial radial distribution functions and orientational correlations of the real system at a semi-quantitative level.