A Theoretical Assessment of Factors Causing Different Molecular Volumes in Isotopologues

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• 作者：Ricard Gelabert ; Miquel Moreno ; Jos M. Lluch
• 刊名：Journal of Physical Chemistry A
• 出版年：2009
• 出版时间：December 24, 2009
• 年：2009
• 卷：113
• 期：51
• 页码：14161-14169
• 全文大小：223K
• 年卷期：v.113,no.51(December 24, 2009)
• ISSN：1520-5215

文摘

A dynamical study has been performed to determine from first principles the molecular volume of C₆H₆ and C₆D₆ in the gas phase, starting from a normal-mode analysis and using anharmonic potential energy profiles at DFT level to determine vibrational eigenfunctions for all 30 degrees of freedom and using a Monte Carlo procedure to determine the appreciable ranges of variation of the coordinates of all atoms. The gas phase study reveals that the intrinsic volume of C₆D₆ is always the smallest, even though it increases faster with temperature than that of C₆H₆. In order to explain the experimentally observed fact that C₆D₆ volume is the largest at hight temperatures, the likely effect on molecular motions caused by the crystalline environment of a given molecule has to be considered.