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Assessing the electric-field approximation to IR and Raman spectra of dilute HOD in D2O.

Authors :
Ljungberg, Mathias P.
Lyubartsev, A. P.
Nilsson, Anders
Pettersson, Lars G. M.
Source :
Journal of Chemical Physics; 7/21/2009, Vol. 131 Issue 3, p034501, 12p, 2 Charts, 8 Graphs
Publication Year :
2009

Abstract

We analyze the validity of the commonly used electric-field (E-field) approximation to vibrational OH stretch Raman spectra of dilute HOD in D<subscript>2</subscript>O by computing the OH stretch frequency of all molecules in several different structure models, each containing around 2000 molecules. The calculations are done at the B3LYP level using clusters containing 32 molecules centered around the molecule for which the frequencies are calculated; the large cluster size is required due to significant nonlocal contributions influencing the computed frequencies. The vibrational frequencies are determined using a six-point potential optimized discrete variable representation. Raman and infrared intensities are furthermore computed to generate the spectra. We find that a quadratic fit of E-field versus frequency gives a reasonable representation of the calculated distribution of frequencies. However, the mapping depends significantly on the structural model and is thus not universal. Anharmonic couplings are calculated for several optimized clusters showing a general trend to compress the computed frequency distributions, which is in agreement with dynamical simulations (motional narrowing). [ABSTRACT FROM AUTHOR]

Details

Language :
English
ISSN :
00219606
Volume :
131
Issue :
3
Database :
Complementary Index
Journal :
Journal of Chemical Physics
Publication Type :
Academic Journal
Accession number :
43296111
Full Text :
https://doi.org/10.1063/1.3154144