Pressure dependence of the liquid structure and the Raman noncoincidence
effect of liquid methanol revisited
H. Torii
Department of Chemistry, School of Education, Shizuoka
University, 836 Ohya, Shizuoka 422-8529, Japan
Abstract:
Pressure dependence of the liquid structure and the Raman noncoincidence
effect of liquid methanol is examined with the combination of molecular
dynamics (MD) simulations and the intermolecular resonant vibrational
interactions determined by the transition dipole coupling (TDC) mechanism
(MD/TDC method). It is shown that the observed decrease of the Raman
noncoincidence nNCE of the CO
stretching band with increasing density reported in the literature is
quantitatively reproduced by the present calculation. As the density
increases, the hydrogen bonds get slightly shorter, but molecules belonging
to different hydrogen-bond chains get closer to each other to a greater
extent. This anisotropic change in the liquid structure is the reason
for the behavior of nNCE. It is
also shown that the concentration dependence of nNCE
in the methanol/CCl4 binary mixtures reported in a previous study,
and the pressure dependence of nNCE
in methanol may be described in a consistent way as a function of the
number density of methanol in the liquid systems.
*Lecture presented at the European Molecular Liquids
Group (EMLG) Annual Meeting on the Physical Chemistry of Liquids: Novel
Approaches to the Structure, Dynamics of Liquids: Experiments, Theories,
and Simulation,Rhodes, Greece, 7-15 September 2002. Other presentations
are published in this issue, pp. 1-261.
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