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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Anharmonic Vibrational Spectroscopy of Hydrogen-Bonded Systems Directly Computed from ab Initio Potential Surfaces: (H_2O)_n = 2, 3; Cl~-(H_2O)_n, n = 1, 2; H~+(H_2O)_n, n = 1, 2; H_2O-CH_3OH
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Anharmonic Vibrational Spectroscopy of Hydrogen-Bonded Systems Directly Computed from ab Initio Potential Surfaces: (H_2O)_n = 2, 3; Cl~-(H_2O)_n, n = 1, 2; H~+(H_2O)_n, n = 1, 2; H_2O-CH_3OH

机译：从头算势面直接计算的氢键体系的非谐振动光谱：（H_2O）_n = 2，3; Cl〜-（H_2O）_n，n = 1，2; H〜+（H_2O）_n，n = 1，2; H_2O-CH_3OH

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Vibrational energy levels and infrared absorption intensities of several neutral and ionic hydrogen-bonded clusters are computed directly from ab initio potential energy surfaces, and the results are compared with experiment. The electronic structure method used to compute the potential surfaces is MP2, with Dunning's triple-ξ + polarization basis set. The calculation of the vibrational states from the potential surface points is carried out using the correlation corrected vibrational self-consistent field (CC-VSCF) method. This method includes anharmonicity and the coupling between different vibrational modes. The combined electronic structure/vibrational algorithm thus provides first-principles calculations of vibrational spectroscopy at a fairly accurate anharmonic level and can be useful for testing the accuracy of electronic structure methods by comparing with experimental vibrational spectroscopy. Systems treated here are (H_2O)_n, n = 2, 3; Cl~-(H_2O)n, n = 1, 2; H~+(H_2O)_n, n = 1. 2; and H_2O-CH_3OH. In the cases of (H_2O)_3 and H_2O-CH_3OH, over 13 000 potential surface points are computed. For each system treated, all the fundamental transitions are computed, but the experimental data for comparison is mostly available for the OH stretches or other stiff modes only. The results show very good agreement between the calculated and experimental frequencies for all systems. The typical deviation for OH stretching modes is on the order of 50 cm~(-1), indicating that the ab initio potential surface are of good accuracy. This is very encouraging for further pursuing MP2 calculations of potential energy surfaces of hydrogen-bonded systems.
机译：从头算势能面直接计算了几个中性和离子型氢键团簇的振动能级和红外吸收强度，并将结果与​​实验进行了比较。用于计算势能面的电子结构方法是MP2，具有Dunning的Triple-ξ+极化基础。使用相关校正的振动自洽场（CC-VSCF）方法，从潜在的表面点计算振动状态。该方法包括非谐性和不同振动模式之间的耦合。因此，组合的电子结构/振动算法可在相当精确的非谐波水平上提供振动光谱的第一性原理计算，并且可通过与实验振动光谱进行比较来测试电子结构方法的准确性。这里处理的系统是（H_2O）_n，n = 2、3; Cl〜-（H_2O）n，n = 1，2; H〜+（H_2O）_n，n =1。2;和H_2O-CH_3OH。在（H_2O）_3和H_2O-CH_3OH的情况下，计算出超过13000个潜在表面点。对于每个处理的系统，都计算了所有基本跃迁，但是用于比较的实验数据大部分仅适用于OH拉伸或其他刚性模式。结果表明，所有系统的计算频率和实验频率之间都具有很好的一致性。 OH拉伸模式的典型偏差约为50 cm〜（-1），表明从头算势面具有良好的精度。这对于进一步追求氢键系统势能面的MP2计算非常令人鼓舞。

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