Physical Faculty, St. Petersburg State University , Peterhof, St. Petersburg, 198504 Russian Federation.
J Phys Chem A. 2013 Sep 19;117(37):9093-8. doi: 10.1021/jp406569y. Epub 2013 Sep 6.
The equilibrium geometry of the NH3···trans-HONO complex and the harmonic vibrational frequencies and intensities are calculated in the MP2/aug-cc-pVTZ approximation with the basis set superposition error taken into account. Effects of anharmonic interactions on spectroscopic parameters are studied by solving vibrational Schrödinger equations in 1-4 dimensions using the variational method. Anharmonic vibrational equations are formulated in the space of normal coordinates of the complex. Detailed analysis is performed for the H-bond stretching vibration and internal vibrations of the trans-HONO isomer in the complex. The intermode anharmonicity and anharmonic coupling between two, three, and four vibrational modes are studied on the basis of correct ab initio potential energy surfaces calculated in the above approximation. The combinations of normal modes of the complex most strongly coupled to one another are examined. The calculated frequencies and intensities of vibrational bands are compared with the experimental data on the NH3···trans-HONO complex in an argon matrix and results of earlier calculations of monomeric HONO. In this calculation the strong resonance between the first excited state of the OH stretching vibration and the doubly excited state of the NOH bending vibration of trans-HONO isomer in the complex is thoroughly studied by solving vibrational equations in two and four dimensions.
在考虑基组叠加误差的情况下，使用 MP2/aug-cc-pVTZ 近似计算了 NH3···trans-HONO 配合物的平衡几何形状和简谐振动频率和强度。通过使用变分法在 1-4 维空间中求解振动薛定谔方程，研究了非谐相互作用对光谱参数的影响。非谐振动方程是在配合物的正则坐标空间中构建的。详细分析了配合物中 H 键伸缩振动和 trans-HONO 异构体的内部振动。基于在上述近似中计算的正确从头算势能面，研究了两个、三个和四个振动模式之间的互模式非谐性和非谐耦合。检查了与彼此相互作用最强的配合物正则模的组合。计算的振动带的频率和强度与 NH3···trans-HONO 配合物在氩基质中的实验数据和先前对单体 HONO 的计算结果进行了比较。在这项计算中，通过在二维和四维空间中求解振动方程，彻底研究了配合物中 trans-HONO 异构体的 OH 伸缩振动的第一激发态和 NOH 弯曲振动的双重激发态之间的强烈共振。
