1
|
Torrejón MJ, Algaba J, Blas FJ. Dissociation line and driving force for nucleation of the nitrogen hydrate from computer simulation. II. Effect of multiple occupancy. J Chem Phys 2024; 161:054712. [PMID: 39092957 DOI: 10.1063/5.0220098] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2024] [Accepted: 07/17/2024] [Indexed: 08/04/2024] Open
Abstract
In this work, we determine the dissociation line of the nitrogen (N2) hydrate by computer simulation using the TIP4P/Ice model for water and the TraPPE force field for N2. This work is the natural extension of Paper I, in which the dissociation temperature of the N2 hydrate has been obtained at 500, 1000, and 1500 bar [Algaba et al., J. Chem. Phys. 159, 224707 (2023)] using the solubility method and assuming single occupancy. We extend our previous study and determine the dissociation temperature of the N2 hydrate at different pressures, from 500 to 4500 bar, taking into account the single and double occupancy of the N2 molecules in the hydrate structure. We calculate the solubility of N2 in the aqueous solution as a function of temperature when it is in contact with a N2-rich liquid phase and when in contact with the hydrate phase with single and double occupancy via planar interfaces. Both curves intersect at a certain temperature that determines the dissociation temperature at a given pressure. We observe a negligible effect of occupancy on the dissociation temperature. Our findings are in very good agreement with the experimental data taken from the literature. We have also obtained the driving force for the nucleation of the hydrate as a function of temperature and occupancy at several pressures. As in the case of the dissociation line, the effect of occupancy on the driving force for nucleation is negligible. To the best of our knowledge, this is the first time that the effect of the occupancy on the driving force for nucleation of a hydrate that exhibits sII crystallographic structure is studied from computer simulation.
Collapse
Affiliation(s)
- Miguel J Torrejón
- Laboratorio de Simulación Molecular y Química Computacional, CIQSO-Centro de Investigación en Química Sostenible and Departamento de Ciencias Integradas, Universidad de Huelva, 21006 Huelva, Spain
| | - Jesús Algaba
- Laboratorio de Simulación Molecular y Química Computacional, CIQSO-Centro de Investigación en Química Sostenible and Departamento de Ciencias Integradas, Universidad de Huelva, 21006 Huelva, Spain
| | - Felipe J Blas
- Laboratorio de Simulación Molecular y Química Computacional, CIQSO-Centro de Investigación en Química Sostenible and Departamento de Ciencias Integradas, Universidad de Huelva, 21006 Huelva, Spain
| |
Collapse
|
2
|
Michalis VK, Economou IG, Stubos AK, Tsimpanogiannis IN. Phase equilibria molecular simulations of hydrogen hydrates via the direct phase coexistence approach. J Chem Phys 2022; 157:154501. [PMID: 36272800 DOI: 10.1063/5.0108738] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
We report the three-phase (hydrate-liquid water-vapor) equilibrium conditions of the hydrogen-water binary system calculated with molecular dynamics simulations via the direct phase coexistence approach. A significant improvement of ∼10.5 K is obtained in the current study, over earlier simulation attempts, by using a combination of modifications related to the hydrogen model that include (i) hydrogen Lennard-Jones parameters that are a function of temperature and (ii) the water-guest energy interaction parameters optimized further by using the Lorentz-Berthelot combining rules, based on an improved description of the solubility of hydrogen in water.
Collapse
Affiliation(s)
| | - Ioannis G Economou
- Chemical Engineering Program, Texas A&M University at Qatar, P.O. Box 23874, Doha, Qatar
| | - Athanasios K Stubos
- Environmental Research Laboratory, National Center for Scientific Research "Demokritos," 15310 Aghia Paraskevi Attikis, Greece
| | - Ioannis N Tsimpanogiannis
- Chemical Process and Energy Resources Institute (CPERI), Centre for Research & Technology Hellas (CERTH), 57001 Thermi-Thessaloniki, Greece
| |
Collapse
|
3
|
Méndez-Morales T, Montes-Campos H, Pérez-Rodríguez M, Piñeiro MM. Evaluation of hydrogen storage ability of hydroquinone clathrates using molecular simulations. J Mol Liq 2022. [DOI: 10.1016/j.molliq.2022.119487] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
|
4
|
Atamas AA, de Leeuw SW, Cuppen HM. A method distinguishing between guest molecules that can form sI, sII, and sH hydrogen clathrates. RSC Adv 2015. [DOI: 10.1039/c5ra03175c] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
A new method based on free energy calculations is proposed for discriminating between promoters that can form sI, sII, and sH hydrogen clathrates.
Collapse
Affiliation(s)
- Alexander A. Atamas
- Institute for Molecules and Materials
- Radboud University
- 6525 AJ Nijmegen
- The Netherlands
| | - Simon W. de Leeuw
- Leiden Institute of Chemistry
- Gorlaeus Laboratories
- Leiden University
- 2300 RA Leiden
- The Netherlands
| | - Herma M. Cuppen
- Institute for Molecules and Materials
- Radboud University
- 6525 AJ Nijmegen
- The Netherlands
| |
Collapse
|
5
|
Papadimitriou NI, Tsimpanogiannis IN, Economou IG, Stubos AK. Influence of combining rules on the cavity occupancy of clathrate hydrates by Monte Carlo simulations. Mol Phys 2014. [DOI: 10.1080/00268976.2014.902136] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
|
6
|
Ramya K, Venkatnathan A. Characterization of interaction energy and vibrational Raman spectra of nitrogen clathrate hydrates. COMPUT THEOR CHEM 2013. [DOI: 10.1016/j.comptc.2013.09.003] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
|
7
|
Takeuchi F, Hiratsuka M, Ohmura R, Alavi S, Sum AK, Yasuoka K. Water proton configurations in structures I, II, and H clathrate hydrate unit cells. J Chem Phys 2013; 138:124504. [DOI: 10.1063/1.4795499] [Citation(s) in RCA: 141] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
|
8
|
Tsimpanogiannis IN, Papadimitriou NI, Stubos AK. On the limitation of the van der Waals-Platteeuw-based thermodynamic models for hydrates with multiple occupancy of cavities. Mol Phys 2012. [DOI: 10.1080/00268976.2012.666278] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
|
9
|
Alavi S, Ripmeester JA. Nonequilibrium adiabatic molecular dynamics simulations of methane clathrate hydrate decomposition. J Chem Phys 2010; 132:144703. [DOI: 10.1063/1.3382341] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
|
10
|
Rick SW, Freeman DL. Proton disorder and the dielectric constant of type II clathrate hydrates. J Chem Phys 2010; 132:054509. [DOI: 10.1063/1.3294563] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
|
11
|
|
12
|
Alavi S, Susilo R, Ripmeester JA. Linking microscopic guest properties to macroscopic observables in clathrate hydrates: Guest-host hydrogen bonding. J Chem Phys 2009; 130:174501. [DOI: 10.1063/1.3124187] [Citation(s) in RCA: 121] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
|
13
|
Papadimitriou N, Tsimpanogiannis I, Papaioannou A, Stubos A. Monte Carlo study of sII and sH argon hydrates with multiple occupancy of cages. MOLECULAR SIMULATION 2008. [DOI: 10.1080/08927020802101734] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Affiliation(s)
- N.I. Papadimitriou
- a Environmental Research Laboratory , National Center for Scientific Research ‘Demokritos’ , Agia Paraskevi, 15310, Greece
| | - I.N. Tsimpanogiannis
- a Environmental Research Laboratory , National Center for Scientific Research ‘Demokritos’ , Agia Paraskevi, 15310, Greece
| | - A.Th. Papaioannou
- b School of Chemical Engineering, National Technical University of Athens , Zografou, 15780, Greece
| | - A.K. Stubos
- a Environmental Research Laboratory , National Center for Scientific Research ‘Demokritos’ , Agia Paraskevi, 15310, Greece
| |
Collapse
|
14
|
Dornan P, Alavi S, Woo TK. Free energies of carbon dioxide sequestration and methane recovery in clathrate hydrates. J Chem Phys 2007; 127:124510. [PMID: 17902924 DOI: 10.1063/1.2769634] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Classical molecular dynamics simulations are used to compare the stability of methane, carbon dioxide, nitrogen, and mixed CO(2)N(2) structure I (sI) clathrates under deep ocean seafloor temperature and pressure conditions (275 K and 30 MPa) which were considered suitable for CO(2) sequestration. Substitution of methane guests in both the small and large sI cages by CO(2) and N(2) fluids are considered separately to determine the separate contributions to the overall free energy of substitution. The structure I clathrate with methane in small cages and carbon dioxide in large cages is determined to be the most stable. Substitutions of methane in the small cages with CO(2) and N(2) have positive free energies. Substitution of methane with CO(2) in the large cages has a large negative free energy and substitution of the methane in the large cages with N(2) has a small positive free energy. The calculations show that under conditions where storage is being considered, carbon dioxide spontaneously replaces methane from sI clathrates, causing the release of methane. This process must be considered if there are methane clathrates present where CO(2) sequestration is to be attempted. The calculations also indicate that N(2) does not directly compete with CO(2) during methane substitution or clathrate formation and therefore can be used as a carrier gas or may be present as an impurity. Simulations further reveal that the replacement of methane with CO(2) in structure II (sII) cages also has a negative free energy. In cases where sII CO(2) clathrates are formed, only single occupancy of the large cages will be observed.
Collapse
Affiliation(s)
- Peter Dornan
- Centre for Catalysis Research and Innovation, Department of Chemistry, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada
| | | | | |
Collapse
|
15
|
Morales CM, Thompson WH. Mixed Quantum-Classical Molecular Dynamics Analysis of the Molecular-Level Mechanisms of Vibrational Frequency Shifts. J Phys Chem A 2007; 111:5422-33. [PMID: 17580980 DOI: 10.1021/jp071656i] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A detailed analysis of the origins of vibrational frequency shifts of diatomic molecules (I2 and ICl) in a rare gas (Xe) liquid is presented. Specifically, vibrationally adiabatic mixed quantum-classical molecular dynamics simulations are used to obtain the instantaneous frequency shifts and correlate the shifts to solvent configurations. With this approach, important mechanistic questions are addressed, including the following: How many solvent atoms determine the frequency shift? What solvent atom configurations lead to blue shifts, and which lead to red shifts? What is the effect of solute asymmetry? The mechanistic analysis can be generally applied and should be useful in understanding what information is provided by infrared and Raman spectra about the environment of the probed vibrational mode.
Collapse
|
16
|
Alavi S, Ripmeester JA, Klug DD. Molecular dynamics study of the stability of methane structure H clathrate hydrates. J Chem Phys 2007; 126:124708. [PMID: 17411153 DOI: 10.1063/1.2710261] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Molecular dynamics simulations are used to study the stability of structure H (sH) methane clathrate hydrates in a 3 x 3 x 3 sH unit cell replica. Simulations are performed at experimental conditions of 300 K and 2 GPa for three methane intermolecular potentials. The five small cages of the sH unit cell are assigned methane guest occupancies of one and large cage guest occupancies of one to five are considered. Radial distribution functions, unit cell volumes, and configurational energies are studied as a function of large cage CH(4) occupancy. Free energy calculations are carried out to determine the stability of clathrates for large cage occupancies. Large cage occupancy of five is the most stable configuration for a Lennard-Jones united-atom potential and the Tse-Klein-McDonald potential parametrized for condensed methane phases and two for the most stable configuation for the Murad and Gubbins potential.
Collapse
Affiliation(s)
- Saman Alavi
- Department of Chemistry, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada.
| | | | | |
Collapse
|
17
|
Sizov VV, Piotrovskaya EM. Computer Simulation of Methane Hydrate Cage Occupancy. J Phys Chem B 2007; 111:2886-90. [PMID: 17388408 DOI: 10.1021/jp0658905] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Grand canonical Monte Carlo simulation results are presented for bulk sI methane hydrate. The description of hydrogen-bonded clathrate network allows the water molecules to move and rotate. A more idealized rigid structural model based on the van der Waals-Platteeuw (vdWP) theory is used for comparison. Occupancy isotherms and pressure versus temperature occupancy diagrams are computed for temperatures below 260 K and pressures up to 400 bar. It is found that the results obtained with the vdWP-like model are in qualitative agreement with experiment, though this model fails to account for structural transformations of water network in the vicinity of the melting point.
Collapse
Affiliation(s)
- Vladimir V Sizov
- Department of Chemistry, St. Petersburg State University, Universitetskii prospekt, 26, Peterhof, 198504 St. Petersburg, Russia.
| | | |
Collapse
|
18
|
Alavi S, Woo TK. How much carbon dioxide can be stored in the structure H clathrate hydrates?: A molecular dynamics study. J Chem Phys 2007; 126:044703. [PMID: 17286495 DOI: 10.1063/1.2424936] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The stability of structure H (sH) carbon dioxide clathrate hydrates at three temperature-pressure conditions are determined by molecular dynamics simulations on a 3x3x3 sH unit cell replica. Simulations are performed at 100 K at ambient pressure, 273 K at 100 bars and also 300 K and 5.0 kbars. The small and medium cages of the sH unit cell are occupied by a single carbon dioxide guest and large cage guest occupancies of 1-5 are considered. Radial distribution functions are given for guests in the large cages and unit cell volumes and configurational energies are studied as a function of large cage CO(2) occupancy. Free energy calculations are carried out to determine the stability of clathrates for large cage occupancies at three temperature/pressure conditions stated above. At the low temperature, large cage occupancy of 5 is the most stable while at the higher temperature, the occupancy of 3 is the most favored. Calculations are also performed to show that the CO(2) sH clathrate is more stable than the methane clathrate analog. Implications on CO(2) sequestration by clathrate formation are discussed.
Collapse
Affiliation(s)
- Saman Alavi
- Department of Chemistry, University of Ottawa, Ottawa, Ontario KIN 6N5, Canada.
| | | |
Collapse
|
19
|
Alavi S, Ripmeester JA, Klug DD. Stability of rare gas structure H clathrate hydrates. J Chem Phys 2006; 125:104501. [PMID: 16999535 DOI: 10.1063/1.2238864] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Molecular dynamics simulations are used to study the stability of structure H (sH) clathrate hydrates with the rare gases Ne, Ar, Kr, and Xe. Simulations on a 3 x 3 x 3 sH unit cell replica are performed at ambient pressure at 40 and 100 K temperatures. The small and medium (s+m) cages of the sH unit cell are assigned rare gas guest occupancies of 1 and for large (l) cages guest occupancies of 1-6 are considered. Radial distribution functions for guest pairs with occupancies in the l-l, l-(s+m), and (s+m)-(s+m) cages are presented. The unit cell volumes and configurational energies are studied as a function of large cage occupancy for the rare gases. Free energy calculations are carried out to determine the stability of clathrates for large cage occupancies at 100 K and 1 bar and 20 kbar pressures. These studies show that the most stable argon clathrate has five guests in the large cages. For krypton and xenon the most stable configurations have three and two guests in the large cages, respectively.
Collapse
Affiliation(s)
- Saman Alavi
- Steacie Institute for Molecular Sciences, National Research Council of Canada, 100 Sussex Drive, Ottawa, Ontario K1A 0R6, Canada.
| | | | | |
Collapse
|
20
|
Alavi S, Afagh NA, Ripmeester JA, Thompson DL. Molecular Dynamics Simulations ofp-tert-Butylcalix[4]arene with Small Guest Molecules. Chemistry 2006; 12:5231-7. [PMID: 16528789 DOI: 10.1002/chem.200501317] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Classical molecular dynamics simulations were used to study p-tert-butylcalix[4]arene inclusion compounds with xenon, nitrogen, hydrogen, methane, and sulfur dioxide guest molecules. The calixarene units were taken to be rigid and the intermolecular molecular interactions were modeled as a sum of the van der Waals interactions with parameters from the AMBER force field and electrostatic interactions. Simulations of the high-density alpha phase and low-density beta0 phase of p-tert-butylcalix[4]arene were used to test the force field. The predicted densities of the two phases were found to agree with experimental measurements at 173 K to within 5 %. Simulations were performed with guests placed inside the calixarene cages of the beta0 phase. Guest-host ratios of 1:1 to 1:4 were considered. Changes in the unit-cell volume and density of the phases with the addition of guest molecules and the inclusion energies for the guests were determined. Finally, the dynamics of the guest motion inside the cages were characterized by determining the root-mean-square displacements and velocity autocorrelation functions of the xenon and nitrogen guests.
Collapse
Affiliation(s)
- Saman Alavi
- Steacie Institute for Molecular Sciences (SIMS), National Research Council of Canada, 100 Sussex Dr., Ottawa, Ontario K1A 0R6, Canada
| | | | | | | |
Collapse
|
21
|
Daschbach JL, Chang TM, Corrales LR, Dang LX, McGrail P. Molecular Mechanisms of Hydrogen-Loaded β-Hydroquinone Clathrate. J Phys Chem B 2006; 110:17291-5. [PMID: 16942060 DOI: 10.1021/jp062691c] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Molecular dynamics simulations are used to investigate the molecular interactions of hydrogen-loaded beta-hydroquinone clathrate. It is found that, at lower temperatures, higher loadings are more stable, whereas at higher temperatures, lower loadings are more stable. Attractive forces between the guest and host molecules lead to a stabilized minimum-energy configuration at low temperatures. At higher temperatures, greater displacements take the system away from the shallow energy minimum, and the trend reverses. The nature of the cavity structure is nearly spherical for a loading of one, leads to preferential occupation near the hydroxyl ring crowns of the cavity with a loading of two, and at higher loadings, leads to occupation of the interstitial sites (the hydroxyl rings) between cages by a single H(2) molecule with the remaining molecules occupying the equatorial plane of the cavity. Occupation of the interstitial positions of the cavities leads to facile diffusion.
Collapse
|
22
|
Alavi S, Ripmeester JA, Klug DD. Molecular dynamics simulations of binary structure H hydrogen and methyl-tert-butylether clathrate hydrates. J Chem Phys 2006; 124:204707. [PMID: 16774364 DOI: 10.1063/1.2199850] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Binary structure H (sH) hydrogen and methyl-tert-butylether (MTBE) clathrate hydrates are studied with molecular dynamics simulations. Simulations on a 3 x 3 x 3 sH unit cell with up to 4.7 mass % hydrogen gas are run at pressures of 100 bars and 2 kbars at 100 and 273 K. For the small and medium cages of the sH unit cell, H2 guest molecule occupancies of 0, 1 (single occupancy), and 2 (double occupancy) are considered with the MTBE molecule occupying all of the large cages. An increase of the small and medium cage occupancies from 1 to 2 leads to a jump in the unit cell volume and configurational energy. Calculations are also set up with 13, 23, and 89 of the MTBE molecules in the large cages replaced by sets of three to six H2 molecules, and the effects on the configurational energy and volume of the simulation cell are determined. As MTBE molecules are replaced with sets of H2 guests in the large cages, the configurational energy of the unit cell increases. At the lower temperature, the energy and volume of the clathrate are not sensitive to the number of hydrogen guests in the large cages; however, at higher temperatures the repulsions among the H2 guest molecules in the large cages cause an increase in the system energy and volume.
Collapse
Affiliation(s)
- Saman Alavi
- Steacie Institute for Molecular Sciences, National Research Council of Canada, 100 Sussex Drive, Ottawa, Ontario K1A 0R6, Canada.
| | | | | |
Collapse
|
23
|
Alavi S, Ripmeester JA, Klug DD. Molecular-dynamics simulations of binary structure II hydrogen and tetrahydrofurane clathrates. J Chem Phys 2006; 124:14704. [PMID: 16409048 DOI: 10.1063/1.2141506] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The binary structure II hydrogen and tetrahydrofurane (THF) clathrates are studied with molecular-dynamics simulations. Simulations are done at pressures of 120 and 1.013 bars for temperatures ranging from 100 to 273 K. For the small cages of the structure II unit cell, H2 guest molecule occupancies of 0, 16 (single occupancy), and 32 (double occupancy) are considered. THF occupancies of 0-8 in the large cages are studied. For cases in which THF does not occupy all large cages in a unit cell, the remaining large cages can be occupied with sets of four H2 guest molecules. The unit-cell volumes and configurational energies are compared in the different occupancy cases. Increasing the small cage occupancy leads to an increase in the unit-cell volume and thermal-expansion coefficient. Among simulations with the same small cage occupancy, those with the large cages containing 4H2 guests have the largest volumes. The THF guest molecules have a stabilizing effect on the clathrate and the configurational energy of the unit cell decreases linearly as the THF content increases. For binary THF + H2 clathrates, the substitution of the THF molecules in the large cages with sets of 4H2 molecules increases the configurational energy. For the binary clathrates, various combinations of THF and H2 occupancies have similar configurational energies.
Collapse
Affiliation(s)
- Saman Alavi
- Steacie Institute for Molecular Sciences, National Research Council of Canada, 100 Sussex Drive, Ottawa, Ontario K1A 0R6, Canada.
| | | | | |
Collapse
|
24
|
Chihaia V, Adams S, Kuhs WF. Molecular dynamics simulations of properties of a (001) methane clathrate hydrate surface. Chem Phys 2005. [DOI: 10.1016/j.chemphys.2005.05.024] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
|
25
|
Alavi S, Ripmeester JA, Klug DD. Molecular-dynamics study of structure II hydrogen clathrates. J Chem Phys 2005; 123:24507. [PMID: 16050759 DOI: 10.1063/1.1953577] [Citation(s) in RCA: 110] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Molecular-dynamics simulations are used to study the stability of structure II hydrogen clathrates with different H2 guest occupancies. Simulations are done at pressures of 2.5 kbars and 1.013 bars and for temperatures ranging from 100 to 250 K. For a structure II unit cell with 136 water molecules, H2 guest molecule occupancies of 0-64 are studied with uniform occupancies among each type of cage. The simulations show that at 100 K and 2.5 kbars, the most stable configurations have single occupancy in the small cages and quadruple occupancy in the large cages. The optimum occupancy for the large cages decreases as the temperature is raised. Double occupancy in the small cages increases the energy of the structures and causes tetragonal distortion in the unit cell. The spatial distribution of the hydrogen guest molecules in the cages is determined by studying the guest-water and guest-guest radial distribution functions at various temperatures.
Collapse
Affiliation(s)
- Saman Alavi
- Steacie Institute for Molecular Sciences, National Research Council of Canada, 100 Sussex Drive, Ottawa, Ontario K1A 0R6, Canada.
| | | | | |
Collapse
|
26
|
Li S, Shepherd TD, Thompson WH. Simulations of the Vibrational Relaxation of a Model Diatomic Molecule in a Nanoconfined Polar Solvent. J Phys Chem A 2004. [DOI: 10.1021/jp048361e] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Affiliation(s)
- Shenmin Li
- Department of Chemistry, University of Kansas, Lawrence, Kansas 66045-7582, and Department of Chemistry/Physics, Westminster College, Salt Lake City, Utah 84105
| | - Tricia D. Shepherd
- Department of Chemistry, University of Kansas, Lawrence, Kansas 66045-7582, and Department of Chemistry/Physics, Westminster College, Salt Lake City, Utah 84105
| | - Ward H. Thompson
- Department of Chemistry, University of Kansas, Lawrence, Kansas 66045-7582, and Department of Chemistry/Physics, Westminster College, Salt Lake City, Utah 84105
| |
Collapse
|
27
|
Sasaki S, Hori S, Kume T, Shimizu H. Microscopic observation andin situRaman scattering studies on high-pressure phase transformations of a synthetic nitrogen hydrate. J Chem Phys 2003. [DOI: 10.1063/1.1563600] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
|
28
|
|