Monitoring Hydroquinone Clathrates in Molecular Simulation Using Local Bond Order Parameters

Hydroquinone clathrates (HQ clathrates) are highly structured crystalline materials with promising application in carbon separation and sequestration, and also in hydrogen storage. In this study, molecular simulation techniques are employed to analyze the structure of β-HQ clathrates using local bond order parameters. The methodology is based on the definition by Steinhardt and Lechner-Dellago of the averaged bond order parameters, which allow a precise differentiation between solid and liquid phases. Using molecular dynamics simulations, we evaluate the role of guest molecules such as CO₂ and CH₄ in the stability and formation of clathrates. In this study, we determine and test an optimal combination of bond order parameters (<i>q̅</i> ₁₂-<i>q̅</i> ₈) capable of accurately characterizing phase transitions with a classification error of less than 0.001%. The proposed method is able to qualitatively and quantitatively discern the membership of each molecule to the different phases during the crystallization and dissociation processes, demonstrating its effectiveness in the study of the dynamics of HQ clathrate at different pressure and temperature conditions. The results of this work provide a solid and applicable theoretical framework intended to further provide insight into the nucleation process of this system, contributing to its understanding.