Reduced-Dimensional Quantum Computations for the Rotational鈥揤ibrational Dynamics of F鈥?/sup>鈥揅H4 and F鈥?/sup>鈥揅H2D2
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- 作者：Csaba F谩bri ; Attila G. Cs谩sz谩r ; G谩bor Czak贸
- 刊名：The Journal of Physical Chemistry A
- 出版年：2013
- 出版时间：August 15, 2013
- 年：2013
- 卷：117
- 期：32
- 页码：6975-6983
- 全文大小：336K
- 年卷期：v.117,no.32(August 15, 2013)
- ISSN：1520-5215
文摘
Variational rotational鈥搗ibrational quantum chemical computations are performed for the F鈥?/sup>鈥揅H4 and F鈥?/sup>鈥揅H2D2 anion complexes using several reduced-dimensional models in a curvilinear polyspherical coordinate system and utilizing an accurate ab initio potential energy surface (PES). The implementation of the models is made practical by using the general rovibrational code GENIUSH, which constructs the complicated form of the exact rovibrational kinetic energy operator in reduced and full dimensions in any user-specified coordinates and body-fixed frames. A one-dimensional CF stretch, 1D(RCF), a two-dimensional intermolecular bend, 2D(胃,蠁), and a three-dimensional intermolecular, 3D(RCF,胃,蠁), rigid methane model provide vibrational energies for the low-frequency, large-amplitude modes in good agreement with full-dimensional MCTDH results for F鈥?/sup>鈥揅H4. The 2D(胃,蠁) and 3D(RCF,胃,蠁) four-well computations, describing equally the four possible CH鈥揊鈥?/sup> bonds, show that the ground-state tunneling splitting is less than 0.01 cm鈥?. For the hydrogen-bonded CH stretching fundamental a local-mode model is found to have almost spectroscopic accuracy, whereas a harmonic frequency analysis performs poorly. The 2D(胃,蠁) and 3D(RCF,胃,蠁) rotational鈥搗ibrational computations on the Td-symmetric four-well PES reveal that in most cases F鈥?/sup>鈥揅H4 behaves as a semirigid C3v symmetric top. For the degenerate intermolecular bending vibrational states substantial splittings of the rigid rotor levels are observed. For F鈥?/sup>鈥揅H2D2 the rotational levels guide the assignment of the vibrational states to either F鈥?/sup>鈥揌 or F鈥?/sup>鈥揇 connectivity.