Structure and stability of multiply occupied methane clathrate hydrates

Liu, Jinxiang; Liu, Haiying; Xu, Jiafang; Chen, Gang; Zhang, Jun; Wang, Shoushan

doi:10.1016/j.cplett.2015.08.010

Cited by 12 publications

(8 citation statements)

References 35 publications

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“…They suggested that the final structure can be summarized as a mixture of sI and sII motifs, linked by 5 12 6 3 cages. In addition, ab initio calculations can also provide unique insights into crucial aspects of the hydrate nucleation [32][33][34][35][36]. Patchkovsii and Tse [37] studied the thermodynamic stability of hydrogen hydrates with respect to guest occupancy by first-principles quantum chemistry calculations, in accordance with experimental results of Mao et al [13].…”

Section: Introductionmentioning

confidence: 70%

Formation of clathrate cages of sI methane hydrate revealed by ab initio study

Liu

Hou

et al. 2017

Energy

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We studied the formation micro-mechanism of the small and large cages in the nucleation pathway of sI methane hydrate using ab initio calculations. We found that the cage precursor is a pentagonal ring of water molecules plus one methane molecule, which is formed through the attraction of the pentagonal water ring to the methane molecule. Due to the difference of the hydrophobic-hydrophilic effects, the ring expansion mechanism and the layer-separated mechanism are observed for the growth of water faces in the small and large cages, respectively. Further, formation of the small cage is more structurally feasible and will locally prefer in the early stage of nucleation, but the large cages will dominate in the crystalline structure of methane hydrate, attributing to their high stabilization energy.

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Section: Introductionmentioning

confidence: 70%

Formation of clathrate cages of sI methane hydrate revealed by ab initio study

Liu

Hou

et al. 2017

Energy

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“…X-ray and neutron diffraction studies of MH-II have revealed that the host structure of MH-II is stable from 0.9 to 1.8 GPa (Figure b). − The most stable occupancy of the CH 4 molecules in the LL cage is controversial. Molecular dynamics simulation studies suggested that two or five is the most stable. , Their results depended on the choice of the basis set used in the calculations. The structural model where three or five CH 4 molecules multiply occupy the LL cage and the S1 and S2 cages contain one CH 4 molecule explains the diffraction patterns satisfactorily. , In Raman studies, the Raman bands assigned to the phonon modes were unchanged in the same pressure range, but the Raman band of the ν 1 mode split at 1.3 GPa. ,− It was thus suggested that the cage occupancies were changed at 1.3 GPa while maintaining the host sH structure.…”

Section: Introductionmentioning

confidence: 99%

“…Molecular dynamics simulation studies suggested that two or five is the most stable. 15,16 Their results depended on the choice of the basis set used in the calculations. The structural model where three or five CH 4 molecules multiply occupy the LL cage and the S1 and S2 cages contain one CH 4 molecule explains the diffraction patterns satisfactorily.…”

Section: ■ Introductionmentioning

confidence: 99%

Infrared and Raman Spectroscopic Study of Methane Clathrate Hydrates at Low Temperatures and High Pressures: Dynamics and Cage Occupancy of Methane

et al. 2021

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Infrared (IR) absorption and Raman spectra of methane hydrate (MH) were measured at low temperatures and high pressures to reveal the dynamics and cage occupancy of CH4 molecules and the hydration numbers in phases I (MH-I), II (MH-II), and III (MH-III). For the IR spectra of MH-I below 40 K, bands assigned to the rovibrational transition appeared in the wavenumber region of the asymmetric stretching (ν3) mode of CH4 molecules in the M (51262) cages. This is evidence of the quasi-rotor behavior of CH4. The rovibrational bands were also observed in the IR spectra of MH-II below 1.3 GPa and below 40 K. Interestingly, the shapes of the totally symmetric stretching (ν1) and ν3 bands in the Raman and IR spectra of MH-II changed drastically above 1.3 GPa. This suggests that the cage occupancy of the LL (51268) cage changed from one to two via dehydration at 1.3 GPa. The hydration number also changed from 5.38 ± 0.05 to 4.80 ± 0.17 at 1.3 GPa. A doubly occupied state in the LL cage may arise from the formation of a dimer of CH4 molecules.

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“…QM calculation is a routine and reliable way to estimate the stability of host–guest interactions of a gas hydrate. The crystal geometry, host–guest interaction energies (Δ E host–guest ), , vibration frequency, , and stability of the guests residing in host cages have been researched by QM calculations.…”

Section: Introductionmentioning

confidence: 99%

“…Liu et al 17 evaluated the stability of differing amounts of CH 4 residing in 5 12 , 4 3 5 6 6 3 , 5 12 6 2 , 5 12 6 4 , and 5 12 6 8 cages based on density functional theory (DFT). Furthermore, the stabilities of the hydrate clusters were examined based on the cohesive energy and adsorption energy.…”

Section: Introductionmentioning

confidence: 99%

Exploring Guest–Host Interactions in Gas Hydrates: Insights from Quantum Mechanics

et al. 2021

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Gas hydrates are comprised of guest molecules and host cages. The stability of a gas hydrate is determined by the host–guest interactions. In this work, the relationship between the characteristics of the guest molecules and the gas hydrate stability were systematically investigated using quantum mechanics (QM) calculations. The physical components (ΔE exch, ΔE ind, ΔE elst, and ΔE dis) of the host–guest interaction energy (ΔE host–guest) of 21 types of gas hydrate clusters were investigated by symmetry-adapted perturbation theory (SAPT). Correlation analyses revealed that ΔE exch, ΔE ind, ΔE elst, and ΔE dis had good linear relationships with ΔE host–guest. In addition, the molecules (CO2, H2S) with a high value for the electrostatic interaction (ΔE elst) have a distinct characteristic in the host–guest interactions. The molecular electrostatic potential (ESP), van der Waals (vdW) volume, and vdW surface areas were calculated to explore those distinct characteristics. The results show that the molecules with higher maximum (V s,max) points of the ESP values have a higher stabilization in the host–guest interactions. It was concluded that the vdW volumes or vdW surface areas and the V s,max values of the guest molecules are the key factors for the stability of gas hydrates.

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Structure and stability of multiply occupied methane clathrate hydrates

Cited by 12 publications

References 35 publications

Formation of clathrate cages of sI methane hydrate revealed by ab initio study

Formation of clathrate cages of sI methane hydrate revealed by ab initio study

Infrared and Raman Spectroscopic Study of Methane Clathrate Hydrates at Low Temperatures and High Pressures: Dynamics and Cage Occupancy of Methane

Exploring Guest–Host Interactions in Gas Hydrates: Insights from Quantum Mechanics

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