Brady G P, Szabo A, Sharp K A
Dept. of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia 19104-6059, USA.
J Mol Biol. 1996 Oct 25;263(2):123-5. doi: 10.1006/jmbi.1996.0563.
The decomposition of free energies and entropies into components has recently been discussed within the framework of the free energy perturbation (FEP) and thermodynamic integration (TI) methods. In FEP, the cumulant expansion of the excess free energy contains coupling terms in second and higher orders. It is shown here that this expansion can be expressed in terms of temperature derivatives of the mean energy, suggesting a natural decomposition of the free energy into components corresponding to each term in the Hamiltonian. This result is derived in such a way that it establishes the equivalence to a particular form of component analysis based on TI in which all terms in the interaction energy are turned on simultaneously using 1/kT as the coupling parameter.
最近，在自由能微扰（FEP）和热力学积分（TI）方法的框架内讨论了自由能和熵分解为各组分的问题。在FEP中，过量自由能的累积量展开包含二阶及更高阶的耦合项。本文表明，这种展开可以用平均能量的温度导数来表示，这意味着自由能可以自然地分解为与哈密顿量中每一项相对应的组分。该结果的推导方式建立了与基于TI的一种特定形式的组分分析的等价性，在这种分析中，相互作用能中的所有项都使用1/kT作为耦合参数同时开启。
