Miller, Thomas F., III and Clary, David C. (2004) Quantum free energies of the conformers of glycine on an ab initio potential energy surface. Physical Chemistry Chemical Physics, 6 (10). pp. 2563-2571. ISSN 1463-9076 http://resolver.caltech.edu/CaltechAUTHORS:MILpccp04
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The torsional path integral Monte Carlo (TPIMC) technique is used to study the five lowest-energy conformers of glycine. The theoretical method provides an anharmonic and quantum-mechanical description of conformational free energy and is used for the first time with an ab initio potential energy surface. The 3-dimensional torsional potential energy surface of glycine was obtained at the MP2/6-311++G** level of theory and is optimized with respect to the non-torsional degrees of freedom. Calculated conformer populations compare well with those reported in recent matrix-isolation infrared spectroscopy experiments. An additional conformer, not yet observed, is predicted to be heavily populated in the thermal equilibria probed by experiment, and a new explanation for its elusiveness is provided. Quantum effects, such as zero point energy, are found to substantially alter conformer populations, and an algorithm for estimating the role of non-torsional vibrations in the conformational thermodynamics of a molecule is introduced.
|Additional Information:||This journal is © the Owner Societies 2004. Received 13th November 2003, Accepted 2nd February 2004. First published on the web 4th March 2004. T.F.M. and D.C.C acknowledge fellowships from the National Science Foundation and the Leverhulme Trust, respectively. The work was supported by the Oxford Supercomputing Centre and the Engineering and Physical Sciences Research Council. The authors appreciate the helpful comments of Dr. M. Mella, Dr. P.D. Godfrey, Prof. S.G. Stepanian, and Prof. J.P. Simons and his research group. Supporting information available: Tables listing the calculated harmonic frequencies of the glycine conformers.|
|Subject Keywords:||SEEDED SUPERSONIC JETS; MONTE-CARLO METHOD; GASEOUS GLYCINE; LARGE MOLECULES; GAS MATRICES; INITIO; ROTAMERIZATION; RELAXATION; SPECTRUM; CLUSTERS|
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|Deposited On:||25 Jun 2008|
|Last Modified:||26 Dec 2012 10:08|
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