"Determination of a methane intermolecular potential model for use in m" by Richard L. Rowley and Tapani A. Pakkanen
 

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

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

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