The origin of diffuse scattering in crystalline carbon tetraiodide

TL;DR

This study investigates the diffuse scattering in crystalline carbon tetraiodide using neutron diffraction and RMC modeling, revealing molecular libration and specific molecular alignments as the scattering sources.

Contribution

It provides a detailed analysis linking diffuse scattering to molecular libration and specific molecular arrangements in crystalline CI4, using combined experimental and modeling approaches.

Findings

Diffuse scattering originates from molecular libration.

Distinct C-I peak at 4.5 Å due to molecular alignment.

Edge-to-edge and corner-to-face molecular arrangements observed.

Abstract

Total scattering neutron powder diffraction measurements were performed on the tetragonal phase (a=6.4202(5) {\AA}, c=9.5762(12) {\AA}) of $CI_4$. The experiments were followed by Reverse Monte Carlo (for POWder diffraction (RMCPOW)) modeling. Detailed analyses of the resulting particle configurations revealed that the observed diffuse scattering originates from the libration of the molecules. By examining the partial radial distribution functions a distinct carbon-iodine peak at 4.5 {\AA} is found, which appears as a consequence of corner-to-face mutual alignment of two molecules. The occurrence of edge-to-edge alignments is also significant within the first carbon-carbon coordination shell.