Computing the Anharmonic Vibrational Spectrum of UF6 in 15 Dimensions with an Optimized Basis Set and Rectangular Collocation

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• 作者：Sergei Manzhos ; Tucker Carrington ; Laura Laverdure ; Nicholas Mosey
• 刊名：Journal of Physical Chemistry A
• 出版年：2015
• 出版时间：September 10, 2015
• 年：2015
• 卷：119
• 期：36
• 页码：9557-9567
• 全文大小：378K
• ISSN：1520-5215

文摘

The anharmonic vibrational spectrum of UF₆ is computed in full dimensionality directly from ab initio data, i.e., bypassing the construction of a potential energy surface (PES). The vibrational Schr枚dinger equation is solved by fitting parameters of an adaptable basis using a modified version of the rectangular collocation algorithm of Manzhos and Carrington ( J. Chem. Phys. 2013, 139, 051101). The basis functions are products of parametrized Hermite polynomials that impose approximate nodal structure. The Schr枚dinger equation is solved in normal coordinates. The results show that anharmonicity and coupling do noticeably affect the vibrational transitions, shifting them by several cm^鈥?. Although UF₆ has 15 coordinates, we compute hundreds of levels with fewer than 1000 basis functions and about 50鈥?00 ab initio points. It is the efficiency of the basis that makes it possible to forego a PES.