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Phys. Rev. Lett. 91, 140601 (2003) [4 pages]

Equilibrium Free Energies from Nonequilibrium Measurements Using Maximum-Likelihood Methods

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Michael R. Shirts
Department of Chemistry, Stanford University, Stanford, California 94305-5080, USA

Eric Bair and Giles Hooker
Department of Statistics, Stanford University, Stanford, California 94305-4065, USA

Vijay S. Pande
Department of Chemistry, Stanford University, Stanford, California 94305-5080, USA

Received 27 June 2003; published 2 October 2003

We present a maximum likelihood argument for the Bennett acceptance ratio method, and derive a simple formula for the variance of free energy estimates generated using this method. This derivation of the acceptance ratio method, using a form of logistic regression, a common statistical technique, allows us to shed additional light on the underlying physical and statistical properties of the method. For example, we demonstrate that the acceptance ratio method yields the lowest variance for any estimator of the free energy which is unbiased in the limit of large numbers of measurements.

© 2003 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevLett.91.140601
DOI:
10.1103/PhysRevLett.91.140601
PACS:
05.10.–a, 05.70.Ce