Vogt Emil, Bertran Valls Pablo, Kjaergaard Henrik G
Department of Chemistry , University of Copenhagen , Universitetsparken 5 , DK-2100 Copenhagen Ø Copenhagen , Denmark.
J Phys Chem A. 2020 Feb 6;124(5):932-942. doi: 10.1021/acs.jpca.9b10682. Epub 2020 Jan 24.
Absolute OH- and OD-stretching transition intensities have been calculated for a series of alcohols (methanol, ethanol, 2-propanol, 1-propanol, and -butanol) with one-dimensional (1D) and three-dimensional (3D) local mode models. We compare the calculated intensities for the Δ = 1-5 and Δ = 1-3 transitions with experimental values. Potential energy and dipole moment surfaces are calculated at the CCSD(T)-F12a/VDZ-F12 level of theory. The 1D local mode model includes only the OH(D)-stretching mode, whereas the 3D local mode model also includes the CO-stretching and COH(D)-bending modes. We analyze the effect on vibrational intensities of using either a molecule-fixed Eckart frame or a space-fixed Cartesian frame. We find that both Eckart embedding and inclusion of the CO-stretching and COH(D)-bending modes in the local mode model are important for the OH/OD-stretching fundamental transition intensities, but have a minor effect on overtone intensities. The 3D reduced-dimensional local model, when combined with coupled cluster surfaces, accurately predicts OH/OD-stretching transition intensities and wavenumbers, for all alcohols included in this work.
已使用一维（1D）和三维（3D）局部模式模型计算了一系列醇（甲醇、乙醇、2-丙醇、1-丙醇和丁醇）的绝对OH-和OD-伸缩跃迁强度。我们将Δ = 1-5和Δ = 1-3跃迁的计算强度与实验值进行了比较。在CCSD(T)-F12a/VDZ-F12理论水平上计算了势能和偶极矩表面。1D局部模式模型仅包括OH(D)-伸缩模式，而3D局部模式模型还包括C-O伸缩和C-OH(D)-弯曲模式。我们分析了使用分子固定的埃卡特框架或空间固定的笛卡尔框架对振动强度的影响。我们发现，埃卡特嵌入以及在局部模式模型中包含C-O伸缩和C-OH(D)-弯曲模式对于OH/OD-伸缩基频跃迁强度很重要，但对泛音强度影响较小。当与耦合簇表面结合时，3D降维局部模型能够准确预测本研究中所有醇的OH/OD-伸缩跃迁强度和波数。
