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arXiv 2008.13437cond-mat.stat-mech
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自由能差的平衡相等

Equilibrium Equality for Free Energy Difference

Weitao Chen

摘要:

Jarzynski等式(JE)和热力学积分法是计算系统恒温两个平衡态之间自由能差(FED)的常用方法。然而,对于一个大规模的系统,需要产生大量的集成样本来达到高精度,这消耗了大量的计算资源。以往的工作通过引入虚可积系统,尝试用平衡量代替非平衡量,提高了计算恒温下不同平衡态间FED的效率。为了克服以往工作中不能有效计算两个不同温度平衡态的FED的缺点,本文通过推导不同温度状态间FED的等式,再结合不同体积状态间FED的等式,推导出任意两个不同平衡态间FED的平衡等式。本文提出的等式将任意两个平衡态之间的FED表示为一个平衡态的系综平均值,使得只产生一个正则系综就可以确定任意两个平衡态之间的FED,从而大大减少了所需的样本,提高了效率。此外,在不同维数的Toda-Lattice模型中,检验了等式的有效性和效率。

英文摘要:

Jarzynski Equality (JE) and the thermodynamic integration method are conventional methods to calculate free energy difference (FED) between two equilibrium states with constant temperature of a system. However, a number of ensemble samples should be generated to reach high accuracy for a system with large size, which consumes a lot computational resource. Previous work had tried to replace the non-equilibrium quantities with equilibrium quantities in JE by introducing a virtual integrable system and it had promoted the efficiency in calculating FED between different equilibrium states with constant temperature. To overcome the downside that the FED for two equilibrium states with different temperature can't be calculated efficiently in previous work, this article derives out the Equilibrium Equality for FED between any two different equilibrium states by deriving out the equality for FED between states with different temperatures and then combining the equality for FED between states with different volumes. The equality presented in this article expresses FED between any two equilibrium states as an ensemble average in one equilibrium state, which enable the FED between any two equilibrium states can be determined by generating only one canonical ensemble and thus the samples needed are dramatically less and the efficiency is promoted a lot. Plus, the effectiveness and efficiency of the equality are examined in Toda-Lattice model with different dimensions.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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