Clathrate hydrates show wide applications in energy recovery and storage, CO₂ capture and storage, and other sustainable technologies. Water vacancy in clathrate hydrates is a common defect; however, its effects on the mechanical properties of clathrate hydrates, especially CO₂ hydrates, have not been well studied. Herein, the mechanical characteristics of CO₂ hydrates with three different types of water vacancy defects are investigated for the first time through molecular dynamics simulations with several popular water force fields. It turns out that the mechanical properties of CO₂ clathrate hydrate vary with the type of water vacancy and water force field. Upon critical strains, a variety of unconventional cages of 4²5⁸6², 4²5⁸6³, 4²5⁸6⁴, 4¹5¹⁰6², 4¹5¹⁰6³, and 4¹5¹⁰6⁴ form, of which 4¹5¹⁰6² predominates and is identified to be transient and a clathrate intermediate in forming 4²5⁸6², 4²5⁸6³, and 4²5⁸6⁴. Moreover, diverse cage transformations of 5¹²6² ↔ 4¹5¹⁰6³, ↔ 4¹5¹⁰6², ↔ 4²5⁸6³, ↔ 4²5⁸6⁴ and 5¹² ↔ 4¹5¹⁰6², ↔ 4²5⁸6² occur via two distinct transformation mechanisms including insertion/removal and rotation of a pair of water molecules. This study provides new perspectives on the mechanics and microstructural transformations of CO₂ hydrate, which are crucial for evaluating the formation and mechanical stability of CO₂ hydrate-bearing sediments as well as the CO₂ geological storage by hydrate-based technologies.

中文翻译：

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含水空位的 CO2 水合物的机械失稳和笼形转变

笼形水合物在能量回收和储存、CO ₂捕获和储存以及其他可持续技术方面具有广泛的应用。笼形水合物中的缺水是常见的缺陷。然而，它对笼形水合物，尤其是CO ₂水合物的力学性能的影响尚未得到很好的研究。在此，首次通过分子动力学模拟研究了具有三种不同类型水空位缺陷的CO ₂水合物的力学特性，并采用了几种流行的水力场。结果表明，CO ₂笼形水合物的力学性能随水空位类型和水力场的不同而不同。在临界应变时，各种非常规的笼子 4 ²5 ⁸ 6 ² , 4 ² 5 ⁸ 6 ³ , 4 ² 5 ⁸ 6 ⁴ , 4 ¹ 5 ¹⁰ 6 ² , 4 ¹ 5 ¹⁰ 6 ³和 4 ¹ 5 ¹⁰ 6 ⁴形式，其中 4 ¹ 5 ¹⁰ 6 ²占主导地位，并被确定为瞬态和笼形中间体，形成 4 ² 5 ⁸ 6 ² , 4 ² 5 ⁸ 6 ³, 和 4 ² 5 ⁸ 6 ⁴。^{此外，5 12} 6 ² ↔ 4 ¹ 5 ¹⁰ 6 ³ , ↔ 4 ¹ 5 ¹⁰ 6 ² , ↔ 4 ² 5 ⁸ 6 ³ , ↔ 4 ² 5 ⁸ 6 ⁴和 5 ¹² ↔ 4 ¹ 5 ¹⁰ 6的多种笼形变换² , ↔ 4 ² 5 ⁸ 6 ²通过两种不同的转化机制发生，包括一对水分子的插入/去除和旋转。该研究为CO 2 水合物的力学和微观结构转变提供了新的视角_，这对于评估含CO ₂水合物沉积物的形成和力学稳定性以及基于水合物技术的CO ₂地质储存至关重要。