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oai:figshare.com:article/33991939 2026-09-25T04:06:42Z category_1 category_4 category_915 category_12 category_21 category_272 category_873 category_39 category_734 category_69 portal_63 item_type_2 month_year_09_2026

Molecular Insights into the Growth/Dissociation of CH₄ Hydrate under the Calcite Slit-Pore Confinement: Effect of Pore Size Variation Bhavesh Moorjani (19451680) Jhumpa Adhikari (1737928) Samik Kumar Hait (16834551) Biophysics Biochemistry Physical Sciences not elsewhere classified Cell Biology Biotechnology Environmental Sciences not elsewhere classified Chemical Sciences not elsewhere classified Ecology Biological Sciences not elsewhere classified Inorganic Chemistry strong electrostatic interaction hydrogen bond analysis higher energy barrier >, 114218 ), varying pore size smallest pore exhibiting pore size variation pore size shifts 6 nm ), ordered bound water hydrophilic silica slit calcite substrate influences existence md simulations 4 </ sub 3 </ sub although molecular dynamics 588 </ pore tends pore system pore confinement ∼ 6 molecular insights water molecules confined water calcite slit small slit decreasing slit calcite surface simulation observations results indicate remain away relative location nvt ensemble molecule near microscopic origins md study In nature, CH₄ hydrates occur within marine sediments characterized by varying pore size, geometry, and composition, all of which influence hydrate phase transition. Although molecular dynamics (MD) studies of confined hydrates often focus on silicate pores, hydrate reservoirs also contain carbonates, which may exhibit hydrate behaviour distinct from silicates. Hence, in this MD study, we investigate the effect of calcite slit-pore size variation on the dissociation temperature (T₃) of CH₄ hydrate, as well as the dynamics of confined water and methane molecules within calcite pores. To this end, we perform direct phase co-existence MD simulations of CH₄ hydrate confined in calcite slit-pores of three different pore sizes (i.e., ∼3.8, ∼6.2, and ∼8.6 nm), in the NVT ensemble at 270, 280, 290, and 300 K. Our results indicate that decreasing slit-pore size shifts the T₃ range for CH₄ hydrate to lower temperatures, with the smallest pore exhibiting the fastest dissociation. The mechanisms of hydrate cage distortion near the hydrate–calcite surface interface and the formation of the bound interfacial water layer have been elucidated for the small slit-pore system, along with hydrogen bond analysis to explain the microscopic origins of our simulation observations. In contrast to the hydrophilic silica slit-pores studied previously (<i>Fluid Phase Equilibria</i> <b>2025</b>, <i>588</i>, 114218), the CH₄ cluster confined in the calcite slit-pore tends to remain away from the calcite surface. This behavior arises from the strong electrostatic interaction between the calcite surface and water molecules, which creates a layer of ordered bound water. The potential of the mean force calculation reveals that this bound water layer imposes a higher energy barrier for the CH₄ molecule near the calcite surface. The relative location of the CH₄ hydrate with respect to the CH₄ cluster and/or the calcite substrate influences the hydrate growth and dissociation mechanism. 2026-09-25T00:00:00Z Dataset Media 10.1021/acs.langmuir.6c03282.s006 https://figshare.com/articles/media/Molecular_Insights_into_the_Growth_Dissociation_of_CH_sub_4_sub_Hydrate_under_the_Calcite_Slit-Pore_Confinement_Effect_of_Pore_Size_Variation/33991939 CC BY-NC 4.0