jp5b03323_si_001.pdf (3.63 MB)
Infrared and Raman Spectroscopy from Ab Initio Molecular Dynamics and Static Normal Mode Analysis: The C–H Region of DMSO as a Case Study
journal contribution
posted on 2015-07-29, 00:00 authored by Sean A. Fischer, Tyler
W. Ueltschi, Patrick Z. El-Khoury, Amanda
L. Mifflin, Wayne P. Hess, Hong-Fei Wang, Christopher J. Cramer, Niranjan GovindCarbon–hydrogen (C–H)
vibration modes serve as key
probes in the chemical identification of hydrocarbons and in vibrational
sum-frequency generation spectroscopy of hydrocarbons at the liquid/gas
interface. Their assignments pose a challenge from a theoretical viewpoint.
In this work, we present a detailed study of the C–H stretching
region of dimethyl sulfoxide using a new ab initio molecular dynamics
(AIMD) module that we have implemented in NWChem. Through a combination
of AIMD simulations and static normal mode analysis, we interpret
experimental infrared and Raman spectra and explore the role of anharmonic
effects in this system. Comprehensive anharmonic normal mode analysis
of the C–H stretching region casts doubt upon previous experimental
assignments of the shoulder on the symmetric C–H stretching
peak. In addition, our AIMD simulations also show significant broadening
of the in-phase symmetric C–H stretching resonance, which suggests
that the experimentally observed shoulder is due to thermal broadening
of the symmetric stretching resonance.