Sunaga Ayaki, Avila Gustavo, Mátyus Edit
ELTE, Eötvös Loránd University, Institute of Chemistry, Budapest 1117, Hungary.
J Chem Theory Comput. 2024 Aug 30. doi: 10.1021/acs.jctc.4c00647.
Full-dimensional (12D) vibrational states of the methanol molecule (CHOH) have been computed using the GENIUSH-Smolyak approach and the potential energy surface from Qu and Bowman (2013). All vibrational energies are converged better than 0.5 cm with respect to the basis and grid size up to the first overtone of the CO stretch, ca. 2000 cm beyond the zero-point vibrational energy. About 70 torsion-vibration states are reported and assigned. The computed vibrational energies agree with the available experimental data within less than a few cm in most cases, which confirms the good accuracy of the potential energy surface. The computations are carried out using curvilinear normal coordinates with the option of path-following coefficients, which minimize the coupling of the small- and large-amplitude motions. It is important to ensure tight numerical fulfillment of the (M) molecular symmetry for every geometry and coefficient set used to define the curvilinear normal coordinates along the torsional coordinate to obtain a faithful description of degeneracy in this floppy system. The reported values may provide a computational reference for fundamental spectroscopy, astrochemistry, and for the search of the proton-to-electron mass ratio variation using the methanol molecule.
已使用GENIUSH - Smolyak方法和Qu与Bowman（2013年）的势能面计算了甲醇分子（CH₃OH）的全维（12D）振动态。所有振动能量相对于基组和网格大小的收敛性优于0.5 cm⁻¹，直至CO伸缩振动的第一泛音，即超过零点振动能约2000 cm⁻¹。报告并指定了约70个扭转 - 振动状态。在大多数情况下，计算得到的振动能量与现有实验数据的吻合度在几厘米以内，这证实了势能面的良好准确性。计算是使用曲线正规坐标并结合路径跟踪系数选项进行的，该选项可使小振幅和大振幅运动的耦合最小化。对于用于沿扭转坐标定义曲线正规坐标的每个几何结构和系数集，确保严格数值满足（M）分子对称性非常重要，以便在此松弛系统中获得对简并的忠实描述。报告的值可为基础光谱学、天体化学以及使用甲醇分子搜索质子与电子质量比变化提供计算参考。
