Keywords
molecular dynamics, methane, ab initio energies
Abstract
The possibility of obtaining an accurate site-site potential model suitable for use in molecular dynamics (MD) simulations of methane from ab initio calculations has been explored. Counterpoise-corrected (CPC), supermolecule, ab initio energies at the MP2/6-311 + G(2df,2pd) level were computed for eleven relative orientations of two methane molecules as a function of C-C separation distance. C-C, C-H, and H-H interaction parameters in a pairwise-additive, site-site potential model for rigid methane molecules were regressed from the ab initio energies, and the resultant model accurately reproduced the ab initio energies. The model suggests that C-H attractions are dominant in weakly binding the methane dimer. CPC energies for methane trimers, tetramers, and a pentamer were also calculated at the same level. The results indicate that the n-mer energy per pair of interactions monotonically converges with increasing n, but that the assumption of pairwise additivity commonly used in MD simulations is reasonably valid. A limited number of higher-level calculations using MP4/6-311 + G(2df,2pd) and MP4/aug-cc-pVTZ were also performed to investigate the possibility of obtaining the intermolecular potential model from higher accuracy calculations without a substantial increase in computer resources. Results suggest that a Ne-methane probe method is not useful in this regard, but that limited, high-level computations, coupled with more extensive lower-level values, may be used to improve the model at minimal cost.
Original Publication Citation
Rowley, Richard L. and Tapani Pakkanen. "Determination of a methane intermolecular potential model for use in molecular simulations from ab initio calculations." The Journal of Chemical Physics 11 (1999): 3368-3377
BYU ScholarsArchive Citation
Rowley, Richard L. and Pakkanen, Tapani A., "Determination of a methane intermolecular potential model for use in molecular simulations from ab initio calculations" (1999). Faculty Publications. 627.
https://scholarsarchive.byu.edu/facpub/627
Document Type
Peer-Reviewed Article
Publication Date
1999-02-15
Permanent URL
http://hdl.lib.byu.edu/1877/1466
Publisher
AIP
Language
English
College
Ira A. Fulton College of Engineering and Technology
Department
Chemical Engineering
Copyright Status
© 1999 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in The Journal of Chemical Physics and may be found at http://link.aip.org/link/?JCPSA6/110/3368/1
Copyright Use Information
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