Document Detail


Variational formula for the free energy based on incomplete sampling in a molecular simulation.
MedLine Citation:
PMID:  14525064     Owner:  NLM     Status:  PubMed-not-MEDLINE    
Abstract/OtherAbstract:
Finite sampling in free-energy perturbation (FEP) calculations by molecular simulation leads to reproducible systematic errors, with sign shown to depend (in a known way) only on which system governs sampling in the simulation. Thus the result of a FEP calculation can be used as a bound on the true free energy. This inequality is of a wholly different nature from established forms such as the Gibbs-Bogoliubov inequality or the second law, in that its origins relate to the performance of a molecular simulation. If one can identify a suitable reference system having a free energy known as a function of some defining parameter, variational schemes based on the finite-sampling inequalities can be implemented. This idea is demonstrated through calculation of the free energy of a hard-sphere solid by perturbing from harmonic references and of a hard-sphere fluid by perturbing from infinitely polydisperse references. The tightness of the bounds increases with the amount of sampling in the simulation and correlates with the entropy difference between the target and reference systems. The bounds are tightest near the point where the entropy difference is least.
Authors:
Nandou Lu; Jhumpa Adhikari; David A Kofke
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Publication Detail:
Type:  Journal Article     Date:  2003-08-21
Journal Detail:
Title:  Physical review. E, Statistical, nonlinear, and soft matter physics     Volume:  68     ISSN:  1539-3755     ISO Abbreviation:  Phys Rev E Stat Nonlin Soft Matter Phys     Publication Date:  2003 Aug 
Date Detail:
Created Date:  2003-10-03     Completed Date:  2004-02-04     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  101136452     Medline TA:  Phys Rev E Stat Nonlin Soft Matter Phys     Country:  United States    
Other Details:
Languages:  eng     Pagination:  026122     Citation Subset:  -    
Affiliation:
Department of Chemical Engineering, University at Buffalo, The State University of New York, Buffalo, New York 14260-4200, USA.
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