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Torsional path integral Monte Carlo method for the quantum simulation of large molecules

Miller, Thomas F., III and Clary, David C. (2002) Torsional path integral Monte Carlo method for the quantum simulation of large molecules. Journal of Chemical Physics, 116 (19). pp. 8262-8269. ISSN 0021-9606. http://resolver.caltech.edu/CaltechAUTHORS:MILjcp02a

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Abstract

A molecular application is introduced for calculating quantum statistical mechanical expectation values of large molecules at nonzero temperatures. The Torsional Path Integral Monte Carlo (TPIMC) technique applies an uncoupled winding number formalism to the torsional degrees of freedom in molecular systems. The internal energy of the molecules ethane, n-butane, n-octane, and enkephalin are calculated at standard temperature using the TPIMC technique and compared to the expectation values obtained using the harmonic oscillator approximation and a variational technique. All studied molecules exhibited significant quantum mechanical contributions to their internal energy expectation values according to the TPIMC technique. The harmonic oscillator approximation approach to calculating the internal energy performs well for the molecules presented in this study but is limited by its neglect of both anharmonicity effects and the potential coupling of intramolecular torsions


Item Type:Article
Additional Information:©2002 American Institute of Physics. Received 24 October 2001; accepted 12 February 2002. The authors would like to thank Dr. Jianshu Cao and Dr. Seogjoo Jang for their helpful discussions regarding the uncoupled winding number representation of rotational path integrals. T.F.M. gratefully acknowledges financial assistance from the Marshall Aid Commemoration Commission. D.C.C. acknowledges a research fellowship from the Leverhulme Trust. The work was supported by the Engineering and Physical Sciences Research Council.
Subject Keywords:Monte Carlo methods, harmonic oscillators, librational states, quantum statistical mechanics, variational techniques, organic compounds, molecular biophysics, macromolecules
Record Number:CaltechAUTHORS:MILjcp02a
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:MILjcp02a
Alternative URL:http://dx.doi.org/10.1063/1.1467342
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:11037
Collection:CaltechAUTHORS
Deposited By: Archive Administrator
Deposited On:24 Jun 2008
Last Modified:26 Dec 2012 10:08

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