Abstract In this communication, effective cage radii of dodecahedral (D) cages in semiclathrate hydrates are investigated based on van der Waals and Platteeuw model. According to recent findings in semiclathrate hydrate structures, D cages in semiclathrate hydrates have anisotropic shapes which provide unique gas capacity and selectivity under mild temperature and pressure conditions. Since applications of these materials for cool energy storage and gas capture and storage technologies are expected, thermodynamic modeling of the semiclathrate hydrates is an emerging issue. So far, the van der Waals and Platteeuw model which is based on Langmuir adsorption theory has been used for modeling of canonical gas hydrates and semiclathrate hydrates. The model applies spherical cell potential to predict guest gas inclusion in the cages, and each cage is characterized by its radius with sphere approximation. While sizes of D cages in semiclathrate hydrates are quite similar to those in gas hydrates, their shapes are found to be irregularly anisotropic dodecahedra that can provide unique gas capture and storage properties. Therefore, when the van der Waals and Platteeuw model is applied to semiclathrate hydrates, it is necessary to discriminate the D cages in the model from those in canonical gas hydrates. Adjusting D cage radius in spherical cell potential model is a simple and convenient way to describe differences in cage shape between semiclathrate hydrates and canonical gas hydrates. Here, we investigated effective cage radii of D cages in the semiclathrate hydrates based on the conventional cell potential model with sphere approximation. Effective radii of D cages in the semiclathrate hydrates were found to be different from those in canonical gas hydrates. With the presently suggested radii, the conventional cell potential model can predict experimental data for cage occupancy in the semiclathrate hydrates more precisely.

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关于范德瓦尔斯和普拉特模型的半笼形水合物中十二面体笼的有效半径

摘要 在本文中，基于范德华和普拉特模型研究了半笼形水合物中十二面体（D）笼的有效笼半径。根据最近在半包合物结构中的发现，半包合物水合物中的 D 笼具有各向异性的形状，在温和的温度和压力条件下提供独特的气体容量和选择性。由于预计这些材料将应用于冷能储存和气体捕获和储存技术，因此半笼形水合物的热力学建模是一个新兴问题。迄今为止，基于朗缪尔吸附理论的范德华和普拉特模型已被用于典型气体水合物和半笼形水合物的建模。该模型应用球形电池电位来预测笼中的客体气体夹杂物，每个笼子的特征是它的半径与球体近似。虽然半笼形水​​合物中 D 笼的尺寸与气体水合物中的 D 笼的尺寸非常相似，但发现它们的形状是不规则的各向异性十二面体，可以提供独特的气体捕获和储存特性。因此，当范德华和普拉特模型应用于半笼形水合物时，需要将模型中的 D 笼与典型气体水合物中的 D 笼区分开来。在球形单元势模型中调整 D 笼半径是描述半笼形水合物和典型气体水合物之间笼形差异的一种简单方便的方法。在这里，我们基于具有球体近似的常规细胞电位模型研究了半笼形水合物中 D 笼的有效笼半径。发现半笼形水合物中 D 笼的有效半径与典型气体水合物中的不同。使用目前建议的半径，传统的电池电位模型可以更精确地预测半笼形水合物中笼子占用的实验数据。