Concerted Pair Motion Due to Double Hydrogen Bonding: The Formic Acid Dimer Case
Concerted Pair Motion Due to Double Hydrogen Bonding: The Formic Acid Dimer Case
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DOI：
10.1007/s41745-019-00137-5
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发表时间：
2019-11
影响因子：
2.3
通讯作者：
Arman Nejad;M. Suhm
中科院分区：
文献类型：
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作者：
Arman Nejad;M. Suhm
甲酸二聚体作为典型的双氢键气相物种，从两个甲酸分子形成稳定络合物时失去的三个平动自由度和三个转动自由度的角度进行了讨论。回顾了这些强受阻平移和转动的实验表征，以及用不同的电子结构计算和振动模型描述相关的基态振动、它们的组合和它们的热移的尝试。CCSD(T)级谐波处理和MP2级非谐波VPT2校正的组合被证实是显著匹配的。在CCSD(T)质量力场中，可以从经典分子动力学中获得定性正确的振动光谱热位移。详细的分析表明，实验和复合理论处理之间的这种一致性不会受到偶然误差抵消的强烈影响，但在这个模型系统中，对六对或分子间模式及其含意和组合的完全收敛的变分处理将是受欢迎的。
Formic acid dimer as the prototypical doubly hydrogen-bonded gas-phase species is discussed from the perspective of the three translational and the three rotational degrees of freedom which are lost when two formic acid molecules form a stable complex. The experimental characterisation of these strongly hindered translations and rotations is reviewed, as are attempts to describe the associated fundamental vibrations, their combinations, and their thermal shifts by different electronic structure calculations and vibrational models. A remarkable match is confirmed for the combination of a CCSD(T)-level harmonic treatment and an MP2-level anharmonic VPT2 correction. Qualitatively correct thermal shifts of the vibrational spectra can be obtained from classical molecular dynamics in CCSD(T)-quality force fields. A detailed analysis suggests that this agreement between experiment and composite theoretical treatment is not strongly affected by fortuitous error cancellation but fully converged variational treatments of the six pair or intermolecular modes and their overtones and combinations in this model system would be welcome.