Infrared and Raman Spectroscopy from Ab Initio Molecular Dynamics and Static Normal Mode Analysis: The C-H Region of DMSO as a Case Study
Infrared and Raman Spectroscopy from Ab Initio Molecular Dynamics and Static Normal Mode Analysis: The C-H Region of DMSO as a Case Study
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DOI：
10.1021/acs.jpcb.5b03323
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发表时间：
2016-03-03
影响因子：
3.3
通讯作者：
Govind, Niranjan
中科院分区：
文献类型：
--
作者：
Fischer, Sean A.;Ueltschi, Tyler W.;Govind, Niranjan
碳氢（C-H）振动模式在碳氢化合物的化学鉴定和碳氢化合物在液/气界面处的振动和频产生光谱中充当关键探针。他们的任务从理论的角度提出了挑战。在这项工作中，我们提出了一个新的从头算分子动力学（AIMD）模块，我们已经实施了NWChem的二甲基亚砜的C-H伸缩区域的详细研究。通过结合AIMD模拟和静态简正模分析，我们解释了实验红外和拉曼光谱，并探讨了非谐效应在该系统中的作用。C-H伸缩区的综合非谐简正模分析对对称C-H伸缩峰上肩部的先前实验归属提出了质疑。此外，我们的AIMD模拟还显示了同相对称C-H伸缩共振的显著加宽，这表明实验观察到的肩部是由于对称伸缩共振的热加宽。
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.