Predicting mixing free energy using mutual ghosting
Predicting mixing free energy using mutual ghosting
复制标题
使用互重影预测混合自由能
DOI：
10.1039/d2me00109h
复制
发表时间：
2022
影响因子：
3.6
通讯作者：
Milner, Scott T.
中科院分区：
文献类型：
--
作者：
Shetty, Shreya;Agarwala, Puja;Gomez, Enrique D.;Milner, Scott T.
过量混合自由能Δ格克斯决定了混合物的相行为并控制了材料的性质。然而，在模拟中测量Δ格克斯具有挑战性。在此之前，我们开发了一种方法，结合分子动力学（MD）模拟与热力学积分沿着的路径的链的转换预测的Flory Huggins相互作用参数χ的聚合物混合物和嵌段共聚物。然而，当共混物的组成分子在结构上相关时，最好应用该方法。为了克服这一限制，我们已经开发了一种新的方法来预测混合物的Δ格克斯。我们进行模拟，通过逐渐减弱不同物种之间的相互作用来诱导混合物中的相分离。为了计算Δ格克斯，我们测量了改变分离相之间的相互作用和界面能所需的热力学功。我们首先将其应用于标记和未标记的Lennard-Jones（LJ）珠以及标记和未标记的苯的等摩尔混合物来验证我们的方法，这与理想溶液理论非常一致。然后，我们计算了苯和吡啶等摩尔混合物的过量混合自由能，使用联合原子（UA）和全原子（AA）势。我们的结果使用UA电位预测的Δ格克斯值约为实验值的四倍，而使用AA电位给出的结果与实验一致，突出了需要良好的电位，忠实地代表混合物的行为。
The excess free energy of mixing ΔGex governs the phase behavior of mixtures and controls material properties. It is challenging, however, to measure ΔGex in simulations. Previously, we developed a method that combines molecular dynamics (MD) simulations with thermodynamic integration along the path of transformation of chains to predict the Flory Huggins interaction parameter χ for polymer mixtures and block copolymers. However, this method is best applied when the constituent molecules of the blends are structurally related. To overcome this limitation, we have developed a new method to predict ΔGex for mixtures. We perform simulations to induce phase separation within a mixture by gradually weakening the interaction between different species. To compute ΔGex we measure the thermodynamic work required to modify the interactions and the interfacial energy between the separated phases. We validate our method by applying it first to equimolar mixtures of labeled and unlabeled Lennard-Jones (LJ) beads, and labeled and unlabeled benzene, which results in good agreement with ideal solution theory. Then we compute the excess free energy of mixing for equimolar mixtures of benzene and pyridine, using both united-atom (UA) and all-atom (AA) potentials. Our results using UA potentials predict a value for ΔGex about four times the experimental value, whereas using AA potentials gives results consistent with experiment, highlighting the need for good potentials to faithfully represent mixture behavior.