We present hard X-ray and neutron diffraction measurements on the polar fluorocarbons HCF3 and H3CF under supercritical conditions and for a range of molecular densities spanning about a factor of ten. The Levesque-Weiss-Reatto inversion scheme has been used to deduce the site-site potentials underlying the measured partial pair distribution functions. The orientational correlations between adjacent fluorocarbon molecules -- which are characterized by quite large dipole moments but no tendency to form hydrogen bonds -- are small compared to a highly polar system like fluid hydrogen chloride. In fact, the orientational correlations in HCF3 and H3CF are found to be nearly as small as those of fluid CF4, a fluorocarbon with no dipole moment.
@article{arxiv.cond-mat/0006157,
title = {The structure of fluid trifluoromethane and methylfluoride},
author = {J. Neuefeind and H. E. Fischer and W. Schröer},
journal= {arXiv preprint arXiv:cond-mat/0006157},
year = {2009}
}