Endohedral confinement of molecular hydrogen

Soullard, J.; Santamaría, Rubén; Cruz, S. A.

doi:10.1016/j.cplett.2004.04.104

Cited by 28 publications

(24 citation statements)

References 17 publications

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“…Inspection of these values indicates reasonable quantitative agreement between the two models, specially for the SiNe 6 cluster. As expected, the energy values for the infinitely hard-box increase faster than those obtained with the cluster method [14].…”

Section: The Modelsupporting

confidence: 80%

Pressure effects on stopping power of solids for channeled ions

Pathak

Cruz

Soullard

2005

Radiation Effects and Defects in Solids

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Pressure effects on the energy loss of swift channeled ions through silicon are considered. This is accomplished by estimating the changes in orbital charge densities and the corresponding mean ionization potentials, induced by increasing pressure. The bulk density for the compressed material is obtained from available experimental information on the corresponding equation of state for pressures up to 11.3 GPa, beyond which a structural phase transformation occurs. The high pressure is simulated by first caging the individual Si atom in a small spherical volume V and estimated as P = −∂E/∂V , where E is the total electronic energy for a particular confinement volume. The energy is selfconsistently calculated through a recently developed shell-wise version of the Thomas-FermiDirac-Weizsäcker density functional, which compares favorably with ab initio calculations on the basis of a cluster model where the Si atom is surrounded by neon (helium) atoms (in a molecular scheme). The resulting individual electronic shell charge densities are then averaged along planar channels to find the effective charge densities needed in the channeling energy loss calculations for channeled ions. The position dependence of the energy loss in the channels for the free and high-pressure case is calculated for 5 MeV protons and alpha particles along the (1 1 0) planar channels.

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Section: The Modelsupporting

confidence: 80%

Pressure effects on stopping power of solids for channeled ions

Pathak

Cruz

Soullard

2005

Radiation Effects and Defects in Solids

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“…In the absence of more generally appropriate functionals for confined H 2 systems we thus advocate the use of accurately parameterized interatomic potentials as employed herein and further justified in other studies. [2][3][4][5]14 Considering the large number of reported DFT studies on the storage of H 2 within various confining nanostructures and materials using one of the functionals tested herein, [15][16][17][18][19][20][21] it is important that subsequent predictions of H 2 storage capacity and energetics based upon such calculations are viewed critically. To show how the different methods can lead to disparate estimates of H 2 storage capacity we show in Table II As all calculations are effectively performed at zero Kelvin and no zero point energy correction is applied these results should not be thought to give a realistic estimate for the maximum practically achievable H 2 storage capacity in SOD.…”

Section: Resultsmentioning

confidence: 99%

“…[13][14][15] More recently the use of density functional theory ͑DFT͒ has been widespread for estimating the properties of H 2 in confined systems. [15][16][17][18][19][20][21] In such studies the binuclear aspect of the H 2 molecule is explicit and the H 2 -H 2 interaction is provided in an ab initio electronic manner albeit indirectly via the choice of functional. In particular, the DFT method has been often applied to systems of interacting H 2 molecules within the confines of inorganic and organic fullerene cages, 16,17 and of carbon nanotubes, 15,[18][19][20] between graphene sheets, 21 and also to solid phase bulk H 2 .…”

Section: Introductionmentioning

confidence: 99%

“…[15][16][17][18][19][20][21] In such studies the binuclear aspect of the H 2 molecule is explicit and the H 2 -H 2 interaction is provided in an ab initio electronic manner albeit indirectly via the choice of functional. In particular, the DFT method has been often applied to systems of interacting H 2 molecules within the confines of inorganic and organic fullerene cages, 16,17 and of carbon nanotubes, 15,[18][19][20] between graphene sheets, 21 and also to solid phase bulk H 2 . 22,23 In this study we investigate the effects of increasing the hydrogen loading of the confining nanopores of the framework silica material sodalite ͑SOD͒ both with classical calculations employing two different specifically parameterized force-field ͑FF͒ sets, and further by first principles calculations employing periodic DFT with four different functionals.…”

Section: Introductionmentioning

confidence: 99%

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Molecular hydrogen confined within nanoporous framework materials: Comparison of density functional and classical force-field descriptions

et al. 2005

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The effect of confinement on the energetics, structure, and absorption of molecular hydrogen is calculated via systematically increasing the H 2 loading in the relatively inert nanoporous siliceous material sodalite ͑SOD͒. Treatments of both the H 2 -H 2 and H 2 -SOD interactions by both periodic density functional theory ͑DFT͒ employing four different functionals ͑LDA, PW91, PBE, and BLYP͒ and by two accurately parameterized force-field ͑FF͒ sets are critically compared. We find for all loadings of H 2 molecules the results differ significantly depending on the method employed. Through a detailed analysis of the H 2 -H 2 and H 2 -SOD interactions in each case we assess the performance of each method employed. We find that none of the tested functionals appear to give a good overall description of our confined H 2 cluster system and the use of well-parameterized FFs is recommended for obtaining a reasonable physical description of such systems.

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“…Then, by following standard rules of analytical mechanics, the Lagrangian equations of motion are obtained. The model provides a formal framework for the previous studies of the hydrogen gas under the effects of pressure and temperature [4][5][6][7][8][9][10][11]. Contrary to other proposed models, the present model includes a representation of the medium surrounding the system of the confined particles by a direct inclusion of such properties as the structure and rigidity of the container, the viscosity of the fluid forming the surrounding medium, etc., described in terms of mechanical and statistical mechanics axioms.…”

Section: Introductionmentioning

confidence: 99%

Microscopic pressure-cooker model for studying molecules in confinement

2014

Self Cite

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A model for a system of a finite number of molecules in confinement is presented and expressions for determining the temperature, pressure, and volume of the system are derived. The present model is a generalisation of the Zwanzig-Langevin model because it includes pressure effects in the system. It also has general validity, preserves the ergodic hypothesis, and provides a formal framework for previous studies of hydrogen clusters in confinement. The application of the model is illustrated by an investigation of a set of prebiotic compounds exposed to varying pressure and temperature. The simulations performed within the model involve the use of a combination of molecular dynamics and density functional theory methods implemented on a computer system with a mixed CPU-GPU architecture.

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Endohedral confinement of molecular hydrogen

Cited by 28 publications

References 17 publications

Pressure effects on stopping power of solids for channeled ions

Pressure effects on stopping power of solids for channeled ions

Molecular hydrogen confined within nanoporous framework materials: Comparison of density functional and classical force-field descriptions

Microscopic pressure-cooker model for studying molecules in confinement

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