Feng Edward H, Crooks Gavin E
College of Chemistry, University of California, Berkeley, Berkeley, California 94720, USA.
Phys Rev E Stat Nonlin Soft Matter Phys. 2009 Jan;79(1 Pt 1):012104. doi: 10.1103/PhysRevE.79.012104. Epub 2009 Jan 29.
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.
热力学长度是一种路径函数，它将长度的概念推广到热力学状态的表面。在这里，我们展示了如何在远离平衡的实验中使用功涨落关系来测量热力学长度。对于这些微观系统，事实证明有必要根据费希尔信息来定义热力学长度。因此，热力学长度可以直接与围绕平衡的涨落幅度相关联。功涨落关系将系统受到外部扰动期间的功与自由能变化联系起来。我们利用这一结果来确定系统处于非平衡状态的实验方案中间点处的平衡平均值。这使我们能够扩展贝内特方法，以在单分子实验中确定平均力势以及热力学长度。
