Mechanical properties and cage transformations in CO 2 -CH 4 heterohydrates: a molecular dynamics and machine learning study

作者：Yu Zhang, Xintong Liu, Qiao Shi, Yongxiao Qu, Yongchao Hao, Yuequn Fu, Jianyang Wu, Zhisen Zhang · 发表于：Journal of Physics D Applied Physics · 年份：2024 · DOI：10.1088/1361-6463/ad6dcf · 被引用次数：26 · 研究领域：Methane Hydrates and Related Phenomena、Quantum, superfluid, helium dynamics、Spacecraft and Cryogenic Technologies

Abstract The substitution of natural gas hydrates with CO 2 offers a compelling dual advantage by enabling the extracting of CH 4 while simultaneously sequestering CO 2 . This process, however, is intricately tied to the mechanical stability of CO 2 -CH 4 heterohydrates. In this study, we report the mechanical properties and cage transformations in CO 2 -CH 4 heterohydrates subjected to uniaxial straining via molecular dynamics (MD) simulations and machine learning (ML). Results indicate that guest molecule occupancy, the ratio of CO 2 to CH 4 and their spatial arrangements within heterohydrate structure greatly dictate the mechanical properties of CO 2 –CH 4 heterohydrates including Young’s modulus, tensile strength, and critical strain. Notable, the introduction of CO 2 within clathrate cages, particularly within 5 12 small cages, weakens the stability of CO 2 –CH 4 heterohydrates in terms of mechanical properties. Upon critical strains, unconventional clathrate cages form, contributing to loading stress oscillation before fracture of heterohydrates. Intriguingly, predominant cage transformations, such as 5 12 6 2 –4 1 5 10 6 3 or 4 2 5 8 6 4 and 5 12 –4 2 5 8 6 1 cages, are identified, in which 4 1 5 10 6 2 appears as primary intermediate cage that is able to transform into 4 1 5 10 6 3 , 4 2 5 8 6 2 , 4 2 5 8 6 3 , 5 12 and 5 12 6 2 cages, unveiling the dynamic nature of heterohydrate structures under straining. Additionally, ML models developed using MD data well predict...