Abstract The stability of CH4, CO2, and H2S in four two-dimensional hydrates, denoted as 2D-I, 2D-II, 2D-III, and 2D-IV, was investigated by the first-principle calculations and molecular dynamics simulations. The result shows that two-dimensional CH4 hydrates are thermodynamically and dynamically stable. CO2 can only form the 2D-I and 2D-II hydrates, while these structures are dynamically unstable. Four two-dimensional H2S hydrates are thermodynamically stable, but only the 2D-I structure is dynamically stable. Further, simulation result suggests that the stability of the two-dimensional hydrate can be increased at low temperatures or in the confined environments (for example, nano-slits). As for the 2D-I binary hydrate, its thermodynamic stability is in between two corresponding pure hydrates, and only the CH4-H2S binary hydrate is dynamically stable. The CH4-CO2-H2S ternary hydrate is dynamically unstable because of the overflow of CO2.

中文翻译：

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二维笼形水合物中 CH4、CO2 和 H2S 的稳定性

摘要 通过第一性原理计算和分子动力学模拟研究了 CH4、CO2 和 H2S 在 2D-I、2D-II、2D-III 和 2D-​​IV 四种二维水合物中的稳定性。结果表明二维CH4水合物在热力学和动力学上是稳定的。CO2 只能形成 2D-I 和 2D-​​II 水合物，而这些结构是动态不稳定的。四种二维 H2S 水合物是热力学稳定的，但只有 2D-I 结构是动态稳定的。此外，模拟结果表明，二维水合物的稳定性可以在低温或受限环境（例如，纳米狭缝）中增加。至于2D-I二元水合物，其热力学稳定性介于两种相应的纯水合物之间，只有 CH4-H2S 二元水合物是动态稳定的。CH4-CO2-H2S三元水合物由于CO2的溢出而动态不稳定。