Abstract
A collection of recent state-of-the-art ab initio results is presefted pertaining to anharmonic vibrational analyses of non-rigid molecules. To demonstrate the performance of electronic structure theory in predicting features of potential energy surfaces to quantitative accuracy, investigations of energy barriers for large-amplitude vibrations in ammonia, isocyanic acid, ethane, and cyclopentene are reported. Anharmonic vibrational analyses based on self-consistent-field and configuration interaction quartic force fields are critically evaluated by focusing on representative results for hydrogen sulfide and nitrous oxide. The use of nonstationary reference structures to improve predictions of anharmonic force fields is reviewed and documented. A summary of an investigation using the complete state-of-the-art armamentarium to elucidate vibrational anharmonicity, vibration-rotation interaction, and the precise r e structure of the quasilinear HNCO molecule is given. Finally, difficulties arising in the application of nonstationary reference geometries in vibrational analyses of large-amplitude motions are highlighted to avert potential pitfalls in future ab initio studies.
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Allen, W.D., East, A.L.L., Császár, A.G. (1993). Ab Initio Anharmonic Vibrational Analyses of Non-Rigid Molecules. In: Laane, J., Dakkouri, M., van der Veken, B., Oberhammer, H. (eds) Structures and Conformations of Non-Rigid Molecules. NATO ASI Series, vol 410. Springer, Dordrecht. https://doi.org/10.1007/978-94-011-2074-6_17
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