title: Infrared and Raman Spectroscopy from Ab Initio Molecular Dynamics and Static Normal Mode Analysis: The C-H Region of DMSO as a Case Study.
abstract: Carbon-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.
authors.affiliation: William R. Wiley Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory , P.O. Box 999, Richland, Washington 99352, United States.
authors.forename: Sean A
authors.initials: SA
authors.lastname: Fischer
authors.affiliation: Department of Chemistry, University of Puget Sound , 1500 North Warner Street, Tacoma, Washington 98416, United States.
authors.forename: Tyler W
authors.initials: TW
authors.lastname: Ueltschi
authors.affiliation: Physical Sciences Division, Pacific Northwest National Laboratory , P.O. Box 999, Richland, Washington 99352, United States.
authors.forename: Patrick Z
authors.initials: PZ
authors.lastname: El-Khoury
authors.affiliation: Department of Chemistry, University of Puget Sound , 1500 North Warner Street, Tacoma, Washington 98416, United States.
authors.forename: Amanda L
authors.initials: AL
authors.lastname: Mifflin
authors.affiliation: Physical Sciences Division, Pacific Northwest National Laboratory , P.O. Box 999, Richland, Washington 99352, United States.
authors.forename: Wayne P
authors.initials: WP
authors.lastname: Hess
authors.affiliation: William R. Wiley Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory , P.O. Box 999, Richland, Washington 99352, United States.
authors.forename: Hong-Fei
authors.initials: HF
authors.lastname: Wang
authors.affiliation: Department of Chemistry, Supercomputing Institute and Chemical Theory Center, University of Minnesota , 207 Pleasant Street South East, Minneapolis, Minnesota 55455, United States.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Cramer
authors.affiliation: William R. Wiley Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory , P.O. Box 999, Richland, Washington 99352, United States.
authors.forename: Niranjan
authors.initials: N
authors.lastname: Govind