Senent M L, Dalbouha S, Cuisset A, Sadovskii D
Departamento de Química y Física Teóricas, Instituto de Estructura de la Materia, IEM-C.S.I.C. , Serrano 121, Madrid 28006, Spain.
Laboratoire de Physico-Chimie de l'Atmosphère, Maison de la Recherche en Environnement Industriel, Université du Littoral - Côte d'Opale , 59140 Dunkerque, France.
J Phys Chem A. 2015 Sep 17;119(37):9644-52. doi: 10.1021/acs.jpca.5b06941. Epub 2015 Sep 3.
The structural and spectroscopic parameters of dimethyl sulfoxide (DMSO) are predicted from CCSD(T)-F12 calculations that can help to resolve the outstanding problem of the rovibrational spectroscopy. DMSO is a near oblate top that presents a trigonal pyramidal geometry. Rotational parameters are determined at the equilibrium and in selected vibrational states. For the ground state, the rotational constants were calculated to be A0 = 7031.7237 MHz, B0 = 6920.1221 MHz, and C0 = 4223.3389 MHz, at few megahertz from the previous experimental measurements. Ab initio calculations allow us to assert that DMSO rotational constants are strongly dependent on anharmonic effects. Asymmetry increases with the vibrational energy. Harmonic frequencies, torsional parameters, and a two-dimensional potential energy surface (2D-PES) focused to describe the internal rotation of the two methyl groups are determined at the CCSD(T)-F12 level of theory. For the medium and small amplitude motions, anharmonic effects are estimated with MP2 theory getting an excellent agreement with experimental data for the ν11 and ν23 fundamentals. Torsional energies and transitions are computed variationally form the 2D-PES that denotes strong interactions between both internal tops. The vibrationally corrected V3 torsional barrier is evaluated to be 965.32 cm(-1). The torsional splitting of the ground vibrational state has been estimated to be lower than 0.01 cm(-1). Although the ν13 torsional fundamental is found at 229.837 cm(-1) in good agreement with previous assessment, there is not accord for the low intense transition ν24. A new assignment predicting ν24 to lie between 190 and 195 cm(-1) is proposed.
通过耦合簇单双激发并包含微扰三重激发（CCSD(T)-F12）计算预测了二甲基亚砜（DMSO）的结构和光谱参数，这些计算有助于解决旋转振动光谱学中悬而未决的问题。DMSO是一个近似扁顶体，呈三角锥形几何结构。在平衡态和选定的振动状态下确定了转动参数。对于基态，计算得到的转动常数为A0 = 7031.7237兆赫兹，B0 = 6920.1221兆赫兹，C0 = 4223.3389兆赫兹，与之前的实验测量值相差仅几兆赫兹。从头算计算使我们能够断言，DMSO的转动常数强烈依赖于非谐效应。不对称性随振动能量增加。在CCSD(T)-F12理论水平上确定了谐波频率、扭转参数以及用于描述两个甲基内旋转的二维势能面（2D-PES）。对于中小振幅运动，用MP2理论估计非谐效应，得到的ν11和ν23基频与实验数据非常吻合。从表示两个内顶部之间强相互作用的2D-PES变分计算扭转能量和跃迁。经振动校正后的V3扭转势垒估计为965.32厘米−1。基态振动状态的扭转分裂估计低于0.01厘米−1。尽管发现ν13扭转基频为229.837厘米−1，与之前的评估结果吻合良好，但对于低强度跃迁ν24却不一致。提出了一个新的归属，预测ν24在190至195厘米−1之间。
