Clathrate hydrates of hydrogen and neon

Dyadin, Yuri A.; Larionov, Eduard G.; Manakov, A. Yu.; Zhurko, F. V.; Aladko, Evgeny Ya.; Mikina, T. V.; Komarov, V. Yu.

doi:10.1070/mc1999v009n05abeh001104

Cited by 248 publications

(206 citation statements)

References 9 publications

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“…The stabilizing impact of THF comes at a cost though, since the promoter molecules occupy a fraction of the large cavities and only the remaining cavities are available for occupancy by hydrogen molecules. Therefore, it is of 4 great importance to study the relationship between potential promoter molecules and the stability of hydrogen hydrates at a wide range of pressures and temperatures.…”

Section: Introductionmentioning

confidence: 99%

Monte Carlo Calculations of the Free Energy of Binary SII Hydrogen Clathrate Hydrates for Identifying Efficient Promoter Molecules

et al. 2013

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The thermodynamics of binary sII hydrogen clathrates with secondary guest molecules is studied with Monte Carlo simulations. The small cages of the sII unit cell are occupied by one H 2 guest molecule.Different promoter molecules entrapped in the large cages are considered. Simulations are conducted at a pressure of 1000 atm in a temperature range of 233 K to 293 K. To determine the stabilizing effect of different promoter molecules on the clathrate, the Gibbs free energy of fully and partially 2 occupied sII hydrogen clathrates are calculated. Our aim is to predict what would be an efficient promoter molecule using properties such as size, dipole moment, and hydrogen bonding capability.The gas clathrate configurational and free energies are compared. The entropy makes a considerable contribution to the free energy and should be taken into account in determining stability conditions of binary sII hydrogen clathrates.3

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Section: Introductionmentioning

confidence: 99%

Monte Carlo Calculations of the Free Energy of Binary SII Hydrogen Clathrate Hydrates for Identifying Efficient Promoter Molecules

et al. 2013

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“…[1][2][3] Nearly two decades ago it was demonstrated that, contrary to the long-held opinion, molecular hydrogen is capable of forming clathrate hydrates. 4,5 Simple hydrogen hydrates, made of only H 2 and H 2 O, adopt the classical structure II (sII).…”

Section: Introductionmentioning

confidence: 99%

Competing quantum effects in the free energy profiles and diffusion rates of hydrogen and deuterium molecules through clathrate hydrates

Cendagorta

Powers

Maršálek

et al. 2016

Phys. Chem. Chem. Phys.

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Clathrate hydrates hold considerable promise as safe and economical materials for hydrogen storage. Here we present a quantum mechanical study of H 2 and D 2 diffusion through a hexagonal face shared by two large cages of clathrate hydrates over a wide range of temperatures. Path integral molecular dynamics simulations are used to compute the free-energy profiles for the diffusion of H 2 and D 2 as a function of temperature. Ring polymer molecular dynamics rate theory, incorporating both exact quantum statistics and approximate quantum dynamical effects, is utilized in the calculations of the H 2 and D 2 diffusion rates in a broad temperature interval. We find that the shape of the quantum free-energy profiles and their height relative to the classical free energy barriers at a given temperature, as well as the rate of diffusion, are profoundly affected by competing quantum effects: above 25 K, zero-point energy (ZPE) perpendicular to the reaction path for diffusion between cavities decreases the quantum rate compared to the classical rate, whereas at lower temperatures tunneling outcompetes the ZPE and as result the quantum rate is greater than the classical rate.

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“…Clathrate hydrates are a group of materials with potential for hydrogen storage, discovered first in 1999 [1]. The hydrogen filled clathrates form so-called structure sII, consisting of two types of cages, i.e.…”

Section: Introductionmentioning

confidence: 99%

Impact of the Confinement on the Intra-Cage Dynamics of Molecular Hydrogen in Clathrate Hydrates

Russina

Kemner

Mezei

2016

MSF

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Abstract.We have studied the diffusive mobility of hydrogen molecules confined in different size cages in clathrate hydrates. In clathrate hydrate H2 molecules are effectively stored by confinement in two different size cages of the nano-porous host structure with accessible volumes of about 0.50 and 0.67 nm diameters, respectively. For the processes of sorption and desorption of the stored hydrogen the diffusive mobility of the molecules plays a fundamental role. In the present study we have focused on the dynamics of the H2 molecules inside the cages as one aspect of global guest molecule mobility across the crystalline host structure. We have found that for the two cage sizes different in diameter by only 34 % and in volume by about a factor of 2.4, the dimension can modify the diffusive mobility of confined hydrogen in both directions, i.e. reducing and surprisingly enhancing mobility compared to the bulk at the same temperature. In the smaller cages of clathrate hydrates hydrogen molecules are localized in the center of the cages even at temperatures >100 K. Confinement in the large cages leads to the onset already at T=10 K of jump diffusion between sorption sites separated from each other by about 2.9 Å at the 4 corners of a tetrahedron. At this temperature bulk hydrogen is frozen at ambient pressure and shows no molecular mobility on the same time scale. A particular feature of this diffusive mobility is the pronounced dynamic heterogeneity: only a temperature dependent fraction of the H2 molecules was found mobile on the time scale covered by the neutron spectrometer used. The differences in microscopic dynamics inside the cages of two different sizes can help to explain the differences in the parameters of macroscopic mobility: trapping of hydrogen molecules in smaller pores matching the molecule size can to play a role in the higher desorption temperature for the small cages.

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Clathrate hydrates of hydrogen and neon

Cited by 248 publications

References 9 publications

Monte Carlo Calculations of the Free Energy of Binary SII Hydrogen Clathrate Hydrates for Identifying Efficient Promoter Molecules

Monte Carlo Calculations of the Free Energy of Binary SII Hydrogen Clathrate Hydrates for Identifying Efficient Promoter Molecules

Competing quantum effects in the free energy profiles and diffusion rates of hydrogen and deuterium molecules through clathrate hydrates

Impact of the Confinement on the Intra-Cage Dynamics of Molecular Hydrogen in Clathrate Hydrates

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