Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California 92093, USA.
Chemistry Department, Queen's University, Kingston, Ontario K7L3N6, Canada.
J Chem Phys. 2018 Mar 14;148(10):102321. doi: 10.1063/1.5005540.
Full-dimensional vibrational spectra are calculated for both X(HO) and X(DO) dimers (X = F, Cl, Br, I) at the quantum-mechanical level. The calculations are carried out on two sets of recently developed potential energy functions (PEFs), namely, Thole-type model energy (TTM-nrg) and many-body energy (MB-nrg), using the symmetry-adapted Lanczos algorithm with a product basis set including all six vibrational coordinates. Although both TTM-nrg and MB-nrg PEFs are derived from coupled-cluster single double triple-F12 data obtained in the complete basis set limit, they differ in how many-body effects are represented at short range. Specifically, while both models describe long-range interactions through the combination of two-body dispersion and many-body classical electrostatics, the relatively simple Born-Mayer functions employed in the TTM-nrg PEFs to represent short-range interactions are replaced in the MB-nrg PEFs by permutationally invariant polynomials to achieve chemical accuracy. For all dimers, the MB-nrg vibrational spectra are in close agreement with the available experimental data, correctly reproducing anharmonic and nuclear quantum effects. In contrast, the vibrational frequencies calculated with the TTM-nrg PEFs exhibit significant deviations from the experimental values. The comparison between the TTM-nrg and MB-nrg results thus reinforces the notion that an accurate representation of both short-range interactions associated with electron density overlap and long-range many-body electrostatic interactions is necessary for a correct description of hydration phenomena at the molecular level.
全维振动光谱分别在量子力学水平上计算了 X(HO) 和 X(DO) 二聚体（X=F、Cl、Br、I）的振动光谱。这些计算是在两组最近开发的势能函数（PEFs）上进行的，即 Thole 型模型能量（TTM-nrg）和多体能量（MB-nrg），使用对称自适应 Lanczos 算法和乘积基集，其中包含所有六个振动坐标。尽管 TTM-nrg 和 MB-nrg PEFs 都是从完全基集限制下获得的耦合簇单双三重 F12 数据中推导出来的，但它们在如何表示短程多体效应方面存在差异。具体来说，尽管两种模型都通过将二体色散和多体经典静电结合来描述远程相互作用，但 TTM-nrg PEFs 中用于表示短程相互作用的相对简单的 Born-Mayer 函数在 MB-nrg PEFs 中被置换不变多项式取代，以实现化学精度。对于所有二聚体，MB-nrg 振动光谱与可用的实验数据非常吻合，正确地再现了非谐和和核量子效应。相比之下，用 TTM-nrg PEFs 计算的振动频率与实验值有显著偏差。因此，TTM-nrg 和 MB-nrg 结果之间的比较进一步证实了这样一种观点，即正确描述分子水平上水化现象需要准确表示与电子密度重叠相关的短程相互作用和远程多体静电相互作用。
