Title: Ab initio intermolecular potential energy surface and second pressure virial coefficients of methane
Authors: Hellmann, Robert 
Bich, Eckard
Vogel, Eckhard
Language: eng
Issue Date: 7-Jun-2008
Document Type: Article
Journal / Series / Working Paper (HSU): The journal of chemical physics : JCP
Volume: 128
Issue: 21
A six-dimensional potential energy hypersurface (PES) for two interacting rigid methane molecules was determined from high-level quantum-mechanical ab initio computations. A total of 272 points for 17 different angular orientations on the PES were calculated utilizing the counterpoise-corrected supermolecular approach at the CCSD(T) level of theory with basis sets of aug-cc-pVTZ and aug-cc-pVQZ qualities. The calculated interaction energies were extrapolated to the complete basis set limit. An analytical site-site potential function with nine sites per methane molecule was fitted to the interaction energies. In addition, a semiempirical correction to the analytical potential function was introduced to take into account the effects of zero-point vibrations. This correction includes adjustments of the dispersion coefficients and of a single-parameter within the fit to the measured values of the second virial coefficient B(T) at room temperature. Quantitative agreement was then obtained with the measured B values over the whole temperature range of the measurements. The calculated B values should definitely be more reliable at very low temperatures (T<150 K) than values extrapolated using the currently recommended equation of state.
Organization Units (connected with the publication): Universität Rostock
ISSN: 00219606
Publisher DOI: 10.1063/1.2932103
Appears in Collections:6 - Bibliographic Data - Publications of the HSU Researchers (before HSU)

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