标题： 旋转不变的局部键序参数用于准确确定水合物结构 显示英文标题

标题： Rotationally invariant local bond order parameters for accurate determination of hydrate structures

摘要： 基于球谐函数的平均局部键序参数，也称为Lechner和Dellago序参数，通常用于分子模拟中确定晶体结构。 在不同的选项中，$\overline{q}_{4}$和$\overline{q}_{6}$参数的组合是文献中最好的选择之一，因为它不仅可以区分固态和液态粒子，还可以区分不同的晶体学相，包括立方相和六方相。 最近，Algaba等人[J. Colloid Interface Sci. 623, 354, (2022)]使用Lechner和Dellago序参数来区分二氧化碳水合物-和液态水分子，在确定二氧化碳水合物-水界面自由能的背景下。 根据结果，之前提到的首选组合并不是区分水合物-和液态水分子的最佳选择。 在本工作中，我们重新审视并扩展了这些参数的使用，以处理水合物相与水液相共存的系统。 我们考虑了具有sI和sII晶体学结构的二氧化碳、甲烷、四氢呋喃、氮和氢的水合物。 我们发现，在所有情况下，$\overline{q}_{3}$和$\overline{q}_{12}$的组合是在大量可能的不同对中最佳的选择，以区分水合物-和液态水分子。 显示英文摘要

摘要： Averaged local bond order parameters based on spherical harmonics, also known as Lechner and Dellago order parameters, are routinely used to determine crystal structures in molecular simulations. Among different options, the combination of the $\overline{q}_{4}$ and $\overline{q}_{6}$ parameters is one of the best choices in the literature since allows one to distinguish, not only between solid- and liquid-like particles but also between different crystallographic phases, including cubic and hexagonal phases. Recently, Algaba et al. [J. Colloid Interface Sci. 623, 354, (2022)] have used the Lechner and Dellago order parameters to distinguish hydrate- and liquid-like water molecules in the context of determining the carbon dioxide hydrate-water interfacial free energy. According to the results, the preferred combination previously mentioned is not the best option to differentiate between hydrate- and liquid-like water molecules. In this work, we revisit and extend the use of these parameters to deal with systems in which clathrate hydrates phases coexist with liquid phases of water. We consider carbon dioxide, methane, tetrahydrofuran, nitrogen, and hydrogen hydrates that exhibit sI and sII crystallographic structures. We find that the $\overline{q}_{3}$ and $\overline{q}_{12}$ combination is the best option possible between a large number of possible different pairs to distinguish between hydrate- and liquid-like water molecules in all cases.