The structure of molecular liquids: neutron diffraction and molecular dynamics simulations
type: CreativeWork
description: Neutron diffraction (ND) measurements on liquid methanol (CD3OD, CD3O(H/D), CD3OH) under ambient conditions were performed to obtain the distinct (intra- + inter-molecular), Gdist (r) and inter-molecular, Ginter(r) radial distribution functions (rdfs) for the three samples. The H/D substitution on hydroxyl-hydrogen (Ho) has been used to extract the partial distribution functions, GXHo(r) (X=C, O, and H - a methyl hydrogen) and GXX (r) at both the distinct and inter-molecular levels from the difference techniques of ND. The O-Ho bond length, which has been the subject of controversy in the past, is found purely from the distinct partial distribution function, GXHo(r) to be 0.98 ± 0.01 Å. The C-H distance obtained from the distinct GXX(r) partial is 1.08 ± 0.01 Å. These distances determined by fitting an intra-molecular model to the total distinct structure functions are 0.961 ± 0.001 Å and 1.096 ± 0.001 Å, respectively. The inter-molecular GXX(r) function, dominated by contributions from the methyl groups, apart from showing broad oscillations extending up to ~14 Å is featureless, mainly because of cancellation effects from six contributing pairs. The Ho....Ho partial pair distribution function (pdf), gHoHo(r), determined from the second order difference, shows that only one other Ho atom can be found within a mean Ho....Ho separation of 2.36 Å. The average position of the O....Ho hydrogen bond determined for the first time purely from experimental inter-molecular GXHo(r) partial distribution function is found to be at 1.75 ± 0.03 Å. The experimental structural results at the partial distribution level are compared with those obtained from molecular dynamics (MD) simulations performed in NVE ensemble by using both 3- and 6-site force field models for the first time in this study. The MD simulations with both the models reproduce the ND rdfs rather well. However, discrepancies begin to appear between the simulated and the experimental partial distribution functions, s…
abstract: Neutron diffraction (ND) measurements on liquid methanol (CD3OD, CD3O(H/D), CD3OH) under ambient conditions were performed to obtain the distinct (intra- + inter-molecular), Gdist (r) and inter-molecular, Ginter(r) radial distribution functions (rdfs) for the three samples. The H/D substitution on hydroxyl-hydrogen (Ho) has been used to extract the partial distribution functions, GXHo(r) (X=C, O, and H - a methyl hydrogen) and GXX (r) at both the distinct and inter-molecular levels from the difference techniques of ND. The O-Ho bond length, which has been the subject of controversy in the past, is found purely from the distinct partial distribution function, GXHo(r) to be 0.98 ± 0.01 Å. The C-H distance obtained from the distinct GXX(r) partial is 1.08 ± 0.01 Å. These distances determined by fitting an intra-molecular model to the total distinct structure functions are 0.961 ± 0.001 Å and 1.096 ± 0.001 Å, respectively. The inter-molecular GXX(r) function, dominated by contributions from the methyl groups, apart from showing broad oscillations extending up to ~14 Å is featureless, mainly because of cancellation effects from six contributing pairs. The Ho....Ho partial pair distribution function (pdf), gHoHo(r), determined from the second order difference, shows that only one other Ho atom can be found within a mean Ho....Ho separation of 2.36 Å. The average position of the O....Ho hydrogen bond determined for the first time purely from experimental inter-molecular GXHo(r) partial distribution function is found to be at 1.75 ± 0.03 Å. The experimental structural results at the partial distribution level are compared with those obtained from molecular dynamics (MD) simulations performed in NVE ensemble by using both 3- and 6-site force field models for the first time in this study. The MD simulations with both the models reproduce the ND rdfs rather well. However, discrepancies begin to appear between the simulated and the experimental partial distribution functions, s…
author: Bianchi, Laurent
language: eng
date published: 2000-5
date modified: 2026-07-24T00:50:23Z
provider: Abertay University
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of Abertay Dundee