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1Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA. spresse@mit.edu
The Journal of Chemical Physics
|February 14, 2006
Summary
Jarzynski's nonequilibrium work relation for free-energy calculations faces sampling challenges. Slow convergence of cumulant expansions for entropic processes requires understanding work distribution tails for accurate free-energy determination.
Area of Science:
- Statistical Mechanics
- Physical Chemistry
- Computational Physics
Background:
- Jarzynski's nonequilibrium work relation provides a method to calculate free-energy differences from nonequilibrium processes.
- The relation involves averaging over system trajectories, often expressed as a cumulant expansion of work.
Purpose of the Study:
- To investigate sampling problems in computing free-energy differences using Jarzynski's nonequilibrium work relation.
- To analyze the scaling of cumulants with phase-space accessibility (epsilon) and particle number (N).
Main Methods:
- Analysis of cumulant expansion convergence for two simple state changes.
- Study of the dependence of cumulants on epsilon and N.
- Examination of the work distribution tails.
Main Results:
- The cumulant expansion exhibits slow convergence for entropic processes where epsilon changes significantly.
- Accurate free-energy calculation necessitates knowledge of the work distribution's tail behavior.
- The validity of Jarzynski's relation depends on the order of limits for N and epsilon.
Conclusions:
- Sampling issues in Jarzynski's relation are linked to the nature of the process (entropic vs. other).
- Understanding work distribution tails is crucial for reliable free-energy computations.
- The applicability of Jarzynski's relation is clarified by considering the limits of particle number and phase-space accessibility.
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