Path-integral virial estimator for reaction rate calculation basedon the quantum instanton aproximation

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The quantum instanton approximation is a type of quantum transition state theory that calculates the chemical reaction rate using the reactive flux correlation function and its low order derivatives at time zero. Here we present several path-integral estimators for the latter quantities, which characterize the initial decay profile of the flux correlation function. As with the internal energy or heat capacity calculation, different estimators yield different variances (and therefore different convergence properties) in a Monte Carlo calculation. Here we obtain a virial(-type) estimator by using a coordinate scaling procedure rather than integration by parts, which allows more computational benefits. We ... continued below

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Yang, Sandy; Yamamoto, Takeshi & Miller, William H. November 28, 2005.

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The quantum instanton approximation is a type of quantum transition state theory that calculates the chemical reaction rate using the reactive flux correlation function and its low order derivatives at time zero. Here we present several path-integral estimators for the latter quantities, which characterize the initial decay profile of the flux correlation function. As with the internal energy or heat capacity calculation, different estimators yield different variances (and therefore different convergence properties) in a Monte Carlo calculation. Here we obtain a virial(-type) estimator by using a coordinate scaling procedure rather than integration by parts, which allows more computational benefits. We also consider two different methods for treating the flux operator, i.e., local-path and global-path approaches, in which the latter achieves a smaller variance at the cost of using second-order potential derivatives. Numerical tests are performed for a one-dimensional Eckart barrier and a model proton transfer reaction in a polar solvent, which illustrates the reduced variance of the virial estimator over the corresponding thermodynamic estimator.

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  • Journal Name: Journal of Chemical Physics; Journal Volume: 124; Journal Issue: 8; Related Information: Journal Publication Date: 02/28/2006

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  • Report No.: LBNL--59146
  • Grant Number: DE-AC02-05CH11231
  • Grant Number: NSF:CHE-0345280
  • Office of Scientific & Technical Information Report Number: 889892
  • Archival Resource Key: ark:/67531/metadc884732

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  • November 28, 2005

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  • Sept. 21, 2016, 2:29 a.m.

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  • Sept. 29, 2016, 3:43 p.m.

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Yang, Sandy; Yamamoto, Takeshi & Miller, William H. Path-integral virial estimator for reaction rate calculation basedon the quantum instanton aproximation, article, November 28, 2005; Berkeley, California. (digital.library.unt.edu/ark:/67531/metadc884732/: accessed September 19, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.