Far-from-equilibrium measurements of thermodynamic length

Edward H. Feng and Gavin E. Crooks
Phys. Rev. E 79, 012104 – Published 29 January 2009

Abstract

Thermodynamic length is a path function that generalizes the notion of length to the surface of thermodynamic states. Here, we show how to measure thermodynamic length in far-from-equilibrium experiments using the work fluctuation relations. For these microscopic systems, it proves necessary to define the thermodynamic length in terms of the Fisher information. Consequently, the thermodynamic length can be directly related to the magnitude of fluctuations about equilibrium. The work fluctuation relations link the work and the free-energy change during an external perturbation on a system. We use this result to determine equilibrium averages at intermediate points of the protocol in which the system is out of equilibrium. This allows us to extend Bennett’s method to determine the potential of the mean force, as well as the thermodynamic length, in single-molecule experiments.

  • Received 9 May 2008

DOI:https://doi.org/10.1103/PhysRevE.79.012104

©2009 American Physical Society

Authors & Affiliations

Edward H. Feng

  • College of Chemistry, University of California, Berkeley, Berkeley, California 94720, USA

Gavin E. Crooks

  • Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA

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Issue

Vol. 79, Iss. 1 — January 2009

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