Comparing Alchemical Free Energy Estimates to Experimental Values Based on the Ben-Naim Formula: How Much Agreement Can We Expect?,The Journal of Physical Chemistry B

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Comparing Alchemical Free Energy Estimates to Experimental Values Based on the Ben-Naim Formula: How Much Agreement Can We Expect?
The Journal of Physical Chemistry B ( IF 2.8 ) Pub Date : 2020-01-10 , DOI: 10.1021/acs.jpcb.9b08965
T Ryan Rogers ₁ , Feng Wang ₁

Affiliation

The solvation free energy (SFE) plays a key role in thermodynamics. One well-established method for computing the SFE is through an alchemical transformation. However, experimental SFEs are generally determined according to the Ben-Naim equations relying on vapor pressure or density ratios. It is important to establish whether, or to what extent, typical alchemical-based free energy computations provide results comparable to experimental SFEs. In this work, we mimic experimental measurements by simulating the liquid-vapor coexistence of water without alchemical operations. The SFEs measured through vapor pressure and density ratios are used to validate the SFEs obtained through alchemical transformations. It is shown that proper consideration of the nonideal behavior of the vapor is important to ensure that the alchemical SFEs are consistent with the Ben-Naim SFEs. Alchemical transformations in the vapor phase should be performed in addition to solution phase transformations for strongly interacting solutes, such as those with low boiling temperatures and large second virial coefficients. A formula based on the virial expansion of pressure is proposed to provide a better estimate of the true SFE from the simulated vapor pressures. The proposed formula is also applicable to experimental determinations of SFE when the pressure-based route is used.

中文翻译：

基于Ben-Naim公式将炼金术的自由能估计值与实验值进行比较：我们可以期待多少协议？

溶剂化自由能（SFE）在热力学中起关键作用。一种成熟的计算SFE的方法是通过炼金术转化。但是，实验性SFE通常是根据Ben-Naim方程确定的，该方程依赖于蒸气压或密度比。重要的是要确定典型的基于炼金术的自由能计算是否提供或可提供与实验性SFE相当的结果。在这项工作中，我们通过模拟水的液体-蒸汽共存而不进行炼金术操作来模拟实验测量。通过蒸气压和密度比测量的SFE用于验证通过炼金术转化获得的SFE。结果表明，正确考虑蒸气的非理想行为对于确保炼金SFE与Ben-Naim SFE一致非常重要。除溶液相转变以实现强相互作用的溶质（例如沸点低且第二维里系数大的溶质）以外，还应进行气相相的化学转化。提出了基于压力的病毒膨胀的公式，以根据模拟的蒸汽压更好地估计真实的SFE。当使用基于压力的路径时，建议的公式也适用于SFE的实验测定。例如沸腾温度低和第二维里系数大的那些。提出了基于压力的病毒膨胀的公式，以根据模拟的蒸汽压更好地估计真实的SFE。当使用基于压力的路径时，建议的公式也适用于SFE的实验测定。例如沸腾温度低和第二维里系数大的那些。提出了基于压力的病毒膨胀的公式，以根据模拟的蒸汽压更好地估计真实的SFE。当使用基于压力的路径时，建议的公式也适用于SFE的实验测定。

更新日期：2020-01-23

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