Hydrate Lattice Research Articles

Two-Dimensional Hydration and Triple-Interlayer Lattice Structures in Sulfate-Intercalated Graphene Oxide Nanosheets

Sulfate anions (SO42−) are pivotal in various scientific and industrial domains, including mineralogy, biology, and materials science. While extensive research has elucidated sulfate hydration in bulk solids, liquids, and gaseous clusters, a significant gap persists in understanding sulfate interactions within two-dimensional materials, particularly graphene oxide (GO) nanosheets. This study investigates the intricate hydration phenomena and novel triple-interlayer lattice configurations that emerge from sulfate intercalation in GO nanosheets. Utilizing a straightforward methodology for obtaining precise X-ray measurements of confined nanospaces, we analyzed the temperature-dependent behavior and structural characteristics of these systems. Our findings reveal how sulfate ions modulate interlayer spacing, the dynamics of GO layers, and phase transitions. This research offers an atomic-scale understanding of hybrid hydration behaviors within confined SO4-H2O nano-environments, advancing our knowledge of sulfate interactions in two-dimensional materials.

Performance variations of light burned magnesia under different calcination parameters and its effects on magnesium oxysulfate cement preparation

This study systematically investigated the impact of different calcination temperatures and holding times on MgO reactivity, as well as the influence of varying reactivity and lattice distortion of MgO on the properties of magnesium oxysulfate cement (MOSC). Results indicated that at temperatures of 700–900℃, magnesite underwent decomposition, resulting in increased lattice distortion, and heightened reactivity. At temperatures of 1000–1100℃, magnesia began sintering, nucleating, and experienced reduced crystal distortion, leading to decreased reactivity. Notably, the appearance of the pseudomorphic mother rock at calcination temperatures of 900℃ and 1000℃ was associated with decreased magnesia reactivity. Moreover, the compressive strength of MOSC prepared using MgO calcined at 900℃ for 6 h increased to 77 MPa after 28 d of air curing. The hydration reactivity and lattice distortion of MgO could be regulated through changing the calcining temperature and holding time, which provided a theoretical basis for the preparation of magnesium oxysulfate cement with excellent mechanical properties.

Modeling on gas hydrate phase equilibrium at high concentration of alcohols

As the major interest in flow assurance of oil and natural gas production, the concentrations of injected alcohols are commonly high exceeding mass fraction of 30 %. In this work, the non-ideality of aqueous phase is represented by the activity coefficient model, in which the water and inhibitor molecules are regarded as associating compounds, and the differences in size and shape between them are properly considered. Coupled with the Chen-Guo hydrate model, the proposed model has been extended to represent the hydrate phase equilibrium of pure gas and gas mixtures in aqueous alcohol solutions with concentrations up to 50 wt%. Moreover, the hydrate lattice parameter was reoptimized to extend the Chen-Guo hydrate model to systems below 273.15 K, when high-concentration of alcohols is present. The predictions of the proposed model have been compared with the experimental data, with the average relative deviations in pressure and temperature of 3.991 % and 0.108 %, respectively, verifying the reliability of this model. Compared with other thermodynamic models or correlations, the proposed model in this work is equivalent to or outperformed those in predicting hydrate formation conditions, especially at high alcohol concentrations.

Adsorption behaviors for clathrate hydrates of CO2 with mixed gases

Here, the preference and adsorption capacities of guest molecules in the sI and sII hydrate of water cages when CO2 + H2S, CO2 + SO2 and CO2 + N2O gas mixture form hydrates are simulated by using grand canonical Monte Carlo and molecular dynamics hybrid simulations method. The results indicate that SO2 prefers to occupy large cages, H2S prefers small cages for CO2 + H2S and CO2 + SO2 and N2O exhibits little preference between small or large or cages of CO2 + N2O sI hydrates, respectively. The abundance ratio shows hydrate can effectively achieve the separation of flue gases. Moreover, the thermodynamics calculation results show that the impurity gases H2S, SO2 and N2O favors the formation of CO2 hydrate. The stability CO2 + H2S, CO2 + SO2 and CO2 + N2O sI hydrates is higher compared to the stability of sII hydrates. The phase equilibrium analysis provides clear evidence that enclathration of H2S and SO2 molecules into the water cages of the hydrate structure plays a crucial role in stabilizing the hydrate lattices. The findings of this study suggest that removal of certain flue gas impurities is not required during the replacement of CH4 in hydrate form with the CO2 gas. The current investigation provides theoretical background for executing replacement of CH4 in hydrate form with the CO2 gas.

Tailoring gas hydrate lattice dimensions for enhanced methane selectivity in biogas upgrading

Gas hydrates, specifically clathrate hydrates, have emerged as a potential separation medium for biogas containing methane (CH4) and carbon dioxide (CO2). However, the efficient separation of CH4 and CO2 remains challenging due to their similar cage occupation behavior within the hydrate structure. This study aimed to enhance CH4 selectivity by modifying the hydrate lattice to exclude CO2 from large cages and reduce the size of small cages through lattice engineering. To achieve this, tert-butyl alcohol (TBA) and trimethylene oxide (TMO) were employed as thermodynamic promoters, inducing strong and weak cage expansion, respectively. The results revealed that TMO hydrates, with their weak cage expansion, exhibited improved CH4 selectivity compared to TBA hydrates, which displayed strong cage expansion due to the larger size of TBA. Multi-stage separation experiments demonstrated that TMO hydrates required four unit stages, while TBA hydrates necessitated more than five unit stages to obtain purified CH4 (> 85%) from an initial gas mixture of CH4 (50%) and CO2 (50%). Additionally, TMO hydrates consistently exhibited higher separation factors than TBA hydrates in all unit stages. The findings emphasize the influence of the thermodynamic promoter's size on the separation performance of gas hydrates in separating CH4 from CH4 + CO2 mixtures. The study provides valuable insights into enhancing CH4 selectivity through lattice engineering and offers guidance in selecting suitable thermodynamic promoters for gas hydrate-based biogas upgrading applications.

A hydrate-based zero liquid discharge method for high-concentration organic wastewater: resource recovery and water reclamation

High-concentration organic wastewater has become a great challenge for wastewater treatment due to its toxicity and non-biodegradability. Traditional water treatment methods focus on removing or destroying organic pollutants rather than considering the high-concentration organic wastewater as a resource. As an ambitious sustainability goal, resource recovery from wastewater to achieve zero liquid discharge (ZLD) has attracted widespread attention. Here, a hydrate-based method is proposed to treat textile wastewater to facilitate the reuse of dyes and enhance water reclamation. The mechanism of interaction between hydrate and organic pollutants was invested. The results show that organic pollutants are rejected from the growing hydrate lattice and concentrated in the residual solution. This method can achieve a max removal efficiency of 93.6% and a water production rate of 80%. In the range of 0–2000 mg/L, the concentration of organic pollutants does not affect the removal effect and water production rate. The concentrated dye can be reused again. The proposed method exhibits potential for recovering resource and clean water from wastewater while achieving ZLD.

Development and Application of a Simulator for Simulating the Behaviors of a Geological System When Replacing CH4 from Hydrate-Bearing Reservoirs by CO2

Conventional techniques for hydrate production may cause the deconstruction of hydrate, changing the geomechanical stresses of the reservoir, which could trigger the subsidence of the seafloor. A new method for replacing CH4 from the hydrate lattice by CO2, without damaging the mechanical structure of sediment, has been proposed. This approach can achieve both the objectives of long-term CO2 sequestration and the safe production of CH4 from hydrates. By coupling the Chen-Guo model into Tough+Hydrate V1.5, an updated simulator CO2-EGHRSim V.10 (CO2 Enhanced Gas Hydrate Recovery simulator) was developed in this work to describe the replacing processes of CH4 from the hydrate lattice by CO2 and to evaluate the storage potential of CO2 and the recovery efficiency of CH4 from the hydrate-bearing reservoirs. The developed simulator was verified using measured data obtained from laboratory experiments. The verification suggested that CO2-EGHRSim performed well in predicting the replacing processes of CH4 with CO2. The simulator was applied to calculate the CO2 storage potential combined with the CH4 recovery from hydrates at the site of Iġnik Sikumi on the North Slope of Alaska. The simulated results indicated that the CO2–CH4 exchange mostly occurred inside the gas plume, and the CO2 hydrate was only present around the production well. The simulated CO2 storage ratio was 0.58, and the CH4 recovery efficiency was 25.95%.

Molecular Dynamics Study of Clathrate-like Ordering of Water in Supersaturated Methane Solution at Low Pressure.

Using molecular dynamics, the evolution of a metastable solution for "methane + water" was studied for concentrations of 3.36, 6.5, 9.45, 12.2, and 14.8 mol% methane at 270 K and 1 bar during 100 ns. We have found the intriguing behavior of the system containing over 10,000 water molecules: the formation of hydrate-like structures is observed at 6.5 and 9.45 mol% concentrations throughout the entire solution volume. This formation of "blobs" and the following amorphous hydrate were studied. The creation of a metastable methane solution through supersaturation is the key to triggering the collective process of hydrate formation under low pressure. Even the first stage (0-1 ns), before the first fluctuating cavities appear, is a collective process of H-bond network reorganization. The formation of fluctuation cavities appears before steady hydrate growth begins and is associated with a preceding uniform increase in the water molecule's tetrahedrality. Later, the constantly presented hydrate cavities become the foundation for a few independent hydrate nucleation centers, this evolution is consistent with the labile cluster and local structure hypotheses. This new mechanism of hydrogen-bond network reorganization depends on the entropy of the cavity arrangement of the guest molecules in the hydrate lattice and leads to hydrate growth.

Ab initio моделирование диэлектрических и оптических свойств льдов I-=SUB=-h-=/SUB=-, I-=SUB=-II-=/SUB=- и решеток гидратов sI, sH

The results of calculating the dielectric and optical characteristics of solid polymorphic phases of water—ices Ih, III and lattices of hydrates sI, sH—are presented. Static dielectric tensors εik and complex frequency-dependent tensors εik(ω) are calculated for these materials. It is shown that, in terms of optical properties, the crystal lattices Ih, III, and sH are uniaxial, the tensor components εxx(ω) and εyy(ω) coincide for them, and the hydrate lattice sI is isotropic. Based on the calculated frequency-dependent dielectric functions εik ′ (ω) and εik ′′ (ω), important optical characteristics were obtained: reflection R(ω), absorption a(ω), loss function L(ω), refractive indices n(ω) and k(ω). Comparison of the dielectric and optical spectra of the sI and sH gratings with the known spectra for methane hydrate sI revealed a broadening of the spectra in the high-energy direction. For the unfilled hydrate sI, a reflection peak was found at an energy of 17.3 eV, the appearance of which is associated with a change in the electronic structure of the crystal in the absence of a methane molecule. Qualitative agreement is obtained between the reflection spectra R(ω) and the functions εik ′ (ω), εik ′′(ω), calculated by quantum mechanical simulation, with experimental spectroscopy data for hexagonal and amorphous ices.

Promoting CH4/CO2 replacement from hydrate with warm brine injection for synergistic energy harvest and carbon sequestration

CH4/CO2 replacement for natural gas hydrates (NGHs) exploitation is a promising method for CO2 geological sequestration and energy recovery simultaneously. However, the puzzles of low replacement efficiency and slow reaction rate caused by the mass transfer obstacle of gas exchange are fatal bottlenecks for field application of gas replacement method. Therefore, we propose a method that uses warm brine injection during CH4/CO2 replacement process to break the barrier of CO2 diffusion and enhance CH4 recovery as well as CO2 storage. Benefiting from the synergistic influence of salt effect and thermal stimulation as well as water flow erosion, warm brine injection provides three dimensionally connected channels in hydrate for subsequent mass transfer, improving CH4/CO2 replacement in the deep layer of hydrate. CO2 sequestration efficiency of the newly proposed method reaches 76.46%, and the maximum amounts of CH4 recovery is nearly treble than that achieved by single CO2 replacement method. Notably, a potential risk of secondary hydrate formation could occur upon the pressure surge and fluid migration attached to warm brine injection, which could be effectively alleviated by increasing salinity to destabilize hydrate lattices by reducing water activity. The gas production is insensitive to the injected heat as the significant heat loss during the transportation of injected brine in pipelines and thermal diffusion through boundaries. The introduction of free water increases the complexity of the reactions in hydrate reservoirs, and the formulation of brine injection regimes should be synergistically optimized based on energy harvest, energy efficiency and CO2 sequestration. This work extends the previous knowledge on CH4/CO2 replacement and shows important practical significance for future field studies of NGHs exploitation and CO2 geological sequestration.

The effect of grainsize of sediments in the CO2/CH4 replacement process within a hydrate lattice: An experimental report

The effects of natural parameters and their related properties, on the formation and dissociation of gas hydrates, have been widely investigated and satisfying information can be found elsewhere in literature. Conversely, there is a substantial lack of similar studies related to CO2/CH4 replacement processes. This research aims to contribute in this sense and shows replacement tests in presence of two pure silica porous media, whose only difference stays in the size of grains. The results confirmed what asserted in literature for the simple formation of hydrates and provided new insights about the replacement process. It was found that the lower size of grains favoured the formation of hydrates and their stability. Precisely for this reason, the fine sediment hindered the replacement, because the higher stability of methane hydrates reduced the capability of CO2 molecules to penetrate within the sediment and take the place of methane molecules. This study proved once again that, natural elements capable to act as promoter for the formation of hydrates, often have an inhibiting effect on the replacement processes.

Hydrogen bond arrangements in (H2O)20, 24, 28 clathrate hydrate cages: Optimization and many-body analysis.

We provide a detailed study of hydrogen bonding arrangements, relative stability, residual entropy, and an analysis of the many-body effects in the (H2O)20 (D-cage), (H2O)24 (T-cage), and (H2O)28 (H-cage) hollow cages making up structures I (sI) and II (sII) of clathrate hydrate lattices. Based on the enumeration of the possible hydrogen bonding networks for a fixed oxygen atom scaffold, the residual entropy (S0) of these three gas phase cages was estimated at 0.754 82, 0.754 44, and 0.754 17 · Nkb, where N is the number of molecules and kb is Boltzmann's constant. A previously identified descriptor of enhanced stability based on the relative arrangement and connectivity of nearest-neighbor fragments on the polyhedral water cluster [strong-weak-effective-bond model] also applies to the larger hollow cages. The three cages contain a maximum of 7, 9, and 11 such preferable arrangements of trans nearest dimer pairs with one "free" OH bond on the donor molecule (t1d dimers). The Many-Body Expansion (MBE) up to the 4-body suggests that the many-body terms vary nearly linearly with the cluster binding energy. Using a hierarchical approach of screening the relative stability of networks starting from optimizations with the TIP4P, TTM2.1-F, and MB-pol classical potentials, subsequently refining at more accurate levels of electronic structure theory (DFT and MP2), and finally correcting for zero-point energy, we were able to identify a group of four low-lying isomers of the (H2O)24 T-cage, two of which are antisymmetric and the other two form a pair of antipode configurations.

Formulating noncovalent interactions to predict structural transition in mixed guest hydrates

AbstractThis work aims at formulating the noncovalent interactions of the mixed guest hydrate lattices of sI and sII structures. The reduced density plots obtained at the B3LYP level with 6‐31G(d) split valence set unveil the crucial contributions of hydrogen bonding, dispersion, van der Waals interaction, and steric effects toward lattice stability. These contributions are rather unreported in the hydrate phase equilibrium modeling. With this research gap, we attempt to formulate the natural regularity in the nonstoichiometric hydrates by the spherical harmonics shape descriptor. The van der Waals and hydrogen‐bond interactions are described with Kihara spherical cell potential and ab initio based calculations, respectively. Further, the ionization potential and polarizability of the guest molecule describe the dispersion interactions. Combining these contributions, we introduce a theoretical framework for the phase equilibrium modeling of mixed guest hydrates. This novel formulation offers various appealing advantages as: significantly reduced parametric structure, standardization of the parameter value for host–host pair, and generalized model framework. Despite of making the proposed theory so simple, it consistently outperforms the existing latest models, which employ various state equations, ab initio based calculations and CSMGem, for a wide variety of systems (total 26 systems tested) with reference to the experimental data.

In-situ Raman study on kinetics behaviors of hydrated bubble in thickening

Natural gas leakage by means of bubbles in cold seep abundantly existed on the ocean floor, causing the change of ocean ecology and the increase of atmospheric temperature. Fortunately, hydrated bubbles as a way of methane sequestration can reduce the effect on the ocean ecology and the escape of gas bubbles from the ocean floor, and are getting attention. To know the growth mode and efficiency of gas hydrate sequestration on bubble, the thickening growth kinetics of hydrated bubble was studied in present work. In-situ Raman spectroscopy was used to analyze the evolution of gas pores and mass transfer channels in the sI CH4, sI CH4-C2H6 and sII CH4-C2H6 hydrate films on the hydrated bubble by the peak area ratio of Raman spectra. Three types of Raman spectra (a-, b-, and c-type), three texture structures of film (Large gas pore; Small gas pore; No gas pore) and two hydrate thickening patterns (filling of new hydrate within large gas pores; covering growth on the original hydrate lattice) were provided in the thickening of hydrated bubble. Results showed that the thickening of the hydrated bubble was a multi-stages growth, i.e., quick growth (stage I), slow growth (stage II), and no growth (stage III). The texture structures and the type and size of gas pore in hydrated bubble were critical for the kinetics growth rate of hydrated bubble in thickening. Especially, the theory of heterogeneous growth of hydrated bubble was proposed to apply the hydrate growth at the interface of two or multi- bubbles, accelerating the efficiency of carbon sequestration as the hydrated bubble. This study will provide a better theoretical basis for understanding the behaviors and efficiency of hydrated carbon sequestration on the surface of bubbles resulting from the gas leakage in the hydrate exploitation or the natural cold seep. SynopsisHydrated bubble strongly modulates the emission of a potent greenhouse gas from the deep sea.

Observation of Electric-Field-Induced Liberation of Guest Molecules from Clathrate Hydrate.

Clathrate hydrates can store a high density of guest molecules in cages. However, as a gas-storage material, the controllable release of guests therefrom is still challenging. Here we report on the utilization of an electric field as a control agent. Attenuated total reflectance surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS) is used to investigate the release of tetrahydrofuran (THF) from the clathrate in the electrochemical double layer (EDL). When voltage is applied, the ATR-SEIRA signal from encaged THF rapidly decreases, and the water characteristic O-H absorption peak exhibits an appreciable blue-shift. Our measurements indicate a transformation of the hydrate lattice to a less H-bonded configuration at the electrode surface. In combination with previous experimental results on the orientation of water molecules in the EDL, we propose that the strong electric field in the EDL aligns the water molecules of the clathrate and distorts the hydrate lattice structure enough to release the trapped guest molecules.

Effect of Gas Exchange Interval on CH4 Recovery Efficiency and Study of Mechanism of CH4 Hydrate Replacement by CO2 Mixture

As an environment-friendly natural gas hydrate exploitation method, CO2 replacement method can not only achieve the purpose of mining natural gas hydrate, but also store the current greenhouse gas CO2 in the form of hydrate on the seabed, and maintain the stratum stability of hydrate deposit area. In order to improve the rate and efficiency of CH4-CO2 replacement reaction, researchers proposed to use CO2 contained gas mixture instead of pure CO2 to replace CH4 in natural gas hydrate. Based our previous work about CH4 hydrate recovery with 40% CO2 + 60% H2, in this study, the effect of gas concentration in gas phase on final CH4 recovery are investigated by implying different time interval of gas exchange operation. Experimental results show that The CH4 recovery efficiency is 10.41 when the gas exchange is continues through the whole replacement process, and CH4 recovery efficiency changes to 12.25, 32.24 and 28.86 when gas exchange operation is carried out every 12, 24, 36 h. Indicating that replaced CH4 needs to be discharged in time to avoid CH4 molecules being replaced to form hydrates again, and it is necessary to accurately control the time interval of gas exchange operation to avoid insufficient contact time between CO2 and H2 molecules and CH4 hydrate, which affects the final replacement efficiency. In addition, the mechanism of CO2 gas mixture containing small gas molecule such as H2, N2 are studied. The results indicate that when CO2 containing small molecules such as H2 and N2 displace CH4 hydrate, the existence of small molecules (H2, N2) can give rise to decompose the hydrate lattice and release CH4 gas. If the gas molecules (CO2, N2, H2, CH4) in the gas phase have enough driving force to enter the hydrate lattice and remain stability, CH4 hydrate will not decompose completely; If not, CH4 hydrate will be completely decomposed.

Incorporation of Ammonium Fluoride and Methanol in Carbon Dioxide Clathrate Hydrates and Their Significance for Hydrate-Based Gas Separation

Methanol is known as one of few small molecules that cannot stabilize a solid clathrate hydrate host lattice as a guest molecule in a simple hydrate phase. Recently, it was discovered that water–NH4F solutions can form clathrates consisting of solid solutions of water and NH4F, which have the same structure as the canonical clathrate hydrates. These doped phases were found to be able to incorporate strongly hydrophilic guests such as methanol. As the next step in testing the utility of these novel hydrates, we prepared NH4F-doped clathrates with simple CO2 and binary CO2 + methanol guest molecules and characterized these by powder X-ray diffraction (PXRD), Raman spectroscopy, and molecular dynamics (MD) simulations. From the PXRD analysis, it was confirmed that CO2 interacts more strongly with the NH4F-doped 512 cages than the 512 cages without dopants. The MD simulations supported the PXRD results by demonstrating a strong interaction between the O atom of CO2 and the dopant NH4+ in the small cages. The incorporation of methanol into the CO2 + methanol clathrates was confirmed by PXRD analysis. With low concentrations of methanol, this guest shows a preference for the 512 cages and may serve as a site blocker for the 512 cage that normally would be occupied by small molecules such as CH4 and N2 in hydrate-based gas separation (HGBS) processes. Phase boundary conditions for hydrate stability in CO2–NH4F–CH3OH– water were obtained, and it was determined that a solution of 5 mol % NH4F and 2.2 mol % CH3OH is a reasonable choice for operating an HBGS process. The present findings provide insight into the potential of the NH4F-doped hydrate lattice, aided by quantities of catalytic methanol, for use in HBGS processes.

Influence of Gas Supply Changes on the Formation Process of Complex Mixed Gas Hydrates.

Natural gas hydrate occurrences contain predominantly methane; however, there are increasing reports of complex mixed gas hydrates and coexisting hydrate phases. Changes in the feed gas composition due to the preferred incorporation of certain components into the hydrate phase and an inadequate gas supply is often assumed to be the cause of coexisting hydrate phases. This could also be the case for the gas hydrate system in Qilian Mountain permafrost (QMP), which is mainly controlled by pores and fractures with complex gas compositions. This study is dedicated to the experimental investigations on the formation process of mixed gas hydrates based on the reservoir conditions in QMP. Hydrates were synthesized from water and a gas mixture under different gas supply conditions to study the effects on the hydrate formation process. In situ Raman spectroscopic measurements and microscopic observations were applied to record changes in both gas and hydrate phase over the whole formation process. The results demonstrated the effects of gas flow on the composition of the resulting hydrate phase, indicating a competitive enclathration of guest molecules into the hydrate lattice depending on their properties. Another observation was that despite significant changes in the gas composition, no coexisting hydrate phases were formed.

Local structure analysis of low-temperature neutron pair distribution function coupled with molecular dynamics simulations of CH4 and CO2 hydrates from 2 to 210 K

CH4 hydrates occur naturally and are an abundant potential fuel source with a corresponding risk of potent greenhouse gas release, due to their stability conditions at low temperature and high pressure. Byproduct CO2 can be exchanged with CH4 in these natural deposits and can potentially stabilize the hydrates at higher temperatures. CH4, CO2, and mixed CH4-CO2 hydrates are studied with in situ neutron pair distribution function experiments from 2 to 210 K to investigate the impact of varying the CH4-CO2 guest composition in the gas hydrate structure. These experiments combined with Reverse Monte Carlo analysis allow for the characterization of intermolecular CH4 and CO2 interactions with the water molecules which form the hydrate lattice and how they impact the local structure of the lattice itself. Results indicate that when CH4 and CO2 co-occupy the hydrate, the host is more strongly distorted than in the pure CH4 and CO2 hydrates, but this becomes less defined with increasing temperature. The presence of CO2 in mixed hydrate increases the stability range and creates a barrier for CH4 to completely leave the structure.

Hydrogen and Deuterium Molecular Escape from Clathrate Hydrates: "Leaky" Microsecond-Molecular-Dynamics Predictions.

It is predicted herewith that the leakage of both hydrogen (H2) and deuterium (D2) from sII clathrate hydrates, borne of guest chemical-potential equalization driving enhanced nonequilibrium intercage hopping, should be observable experimentally. To this end, we have designed simulations to realize and study this process by microsecond molecular dynamics within the temperature range of 150–180 K—for which the hydrate lattice was found to be stable. In this pursuit, we considered initial large-cage (51264) guest occupancies of 1–4, with single occupation of 512 cavities. Examining transient, nonequilibrium intercage hopping, we present a lattice-escape activation energy for the four nominal large-cage occupancies (1–4), by fitting to the hydrate-leakage rate. The intercage hopping of H2 and D2 was studied using Markov-chain models and expressed at different temperatures and large-cage occupancies. The free energy of guest “binding” in the large and small cages was also computed for all of the occupancies. Toward equilibrium, following the majority of H2/D2 escape via leakage, the percentage of occupancies was calculated for both H2 and D2 for all of the systems for all initial nominal large-cage occupancies; here, not unexpectedly, double occupancies occurred more favorably in large cages and single occupancies dominated in small cages.