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dc.contributor.authorSkorpa, Ragnhild
dc.date.accessioned2015-03-12T08:48:51Z
dc.date.available2015-03-12T08:48:51Z
dc.date.issued2014
dc.identifier.isbn978-82-326-0558-3 (printed ver.)
dc.identifier.isbn978-82-326-0559-0 (electronic ver.)
dc.identifier.issn1503-8181
dc.identifier.urihttp://hdl.handle.net/11250/278949
dc.description.abstractThe aim of this thesis project was to model reactions using classical molecular dynamics simulations under both equilibrium and non-equilibrium conditions and to study the effect of the reaction on the transport properties of the system. The dissociation of hydrogen was chosen as a model system based on its importance for the hydrogen society, and the availability of interaction potentials to model the reaction. According to procedures described by Stillinger andWeber, a three-particle interaction potential was added to the pair potential. With this it was possible to properly describe the dissociative reaction. Equilibrium studies was performed at different temperatures and densities. From this, a detailed analysis of the interaction potential, the pair correlation functions and the contributions from the two- and three particle interactions on the overall pressure was performed. This made it possible to determine a temperature and density range where the degree of dissociation was significant. The Small System method was extended to calculate partial molar enthalpies from fluctuations of particles and energies in a subsystem embedded in the simulation box. It was proven that this method worked well for both reacting and nonreacting mixtures. This method was applied to the hydrogen dissociation reaction. From this the reaction enthalpy was determined as a function of temperature, pressure and composition of the reacting mixture for three different densities. The reaction enthalpy was found to be approximately constant (460–440 kJ/mol) for a gas (0.0052 g/cm3), 410–480 kJ/mol for a compressed gas (0.0191 g/cm3) and 500–320 kJ/mol for a liquid (0.0695 g/cm3) for temperatures in the range 4000- 21000 K. With knowledge of the reaction enthalpy, the thermodynamic equilibrium constant, and thus the deviation from ideality was found. Non-equilibrium simulations was used to study the coupled transport of heat and mass both transport of hydrogen through a palladium membrane and for the dissociative reaction in a bulk phase. For the first case, transport coefficients had to be estimated. For the latter case, the coefficients were determined for the first time directly from the fluxes in the system using non-equilibrium molecular dynamics simulations. The transport properties for both systems were then determined from the coefficients. For transport across a membrane, it was illustrated how a temperature gradient could be used to enhance and control the flux of hydrogen through the membranenb_NO
dc.language.isoengnb_NO
dc.publisherNTNUnb_NO
dc.relation.ispartofseriesDoctoral thesis at NTNU;2014:323
dc.relation.haspartPaper 1: Skorpa, Ragnhild; Voldsund, Mari; Takla, Marit; Schnell, Sondre Kvalvåg; Bedeaux, Dick; Kjelstrup, Signe. Assessing the coupled heat and mass transport of hydrogen through a palladium membrane. Journal of Membrane Science 2012 ;Volum 394-395. s. 131-139 <a href="http://dx.doi.org/ 10.1016/j.memsci.2011.12.033" target="_blank"> http://dx.doi.org/ 10.1016/j.memsci.2011.12.033</a>
dc.relation.haspartPaper 2: Skorpa, Ragnhild; Simon, Jean-Marc; Bedeaux, Dick; Kjelstrup, Signe. Equilibrium properties of the reaction H2=2H by classical molecular dynamics simulations. Physical Chemistry, Chemical Physics - PCCP 2014 ;Volum 16.(3) s. 1227-1237 <a href="http://dx.doi.org/ 10.1039/c3cp54149e" target="_blank"> http://dx.doi.org/ 10.1039/c3cp54149e</a>
dc.relation.haspartPaper 3: Schnell, Sondre Kvalvåg; Skorpa, Ragnhild; Bedeaux, Dick; Kjelstrup, Signe; Vlugt, Thijs J.H.; Simon, Jean-Marc. Partial molar enthalpies and reaction enthalpies from equilibrium molecular dynamics simulation. The following article appeared in Journal of Chemical Physics 2014 ;Volum 141.(14) s. 144501 and may be found at <a href="http://dx.doi.org/ 10.1063/1.4896939 " target="_blank"> http://dx.doi.org/ 10.1063/1.4896939 </a>
dc.relation.haspartPaper 4: Skorpa, Ragnhild; Simon, Jean-Marc; Bedeaux, Dick; Kjelstrup, Signe. The reaction enthalpy of hydrogen dissociation calculated with the Small System Method from simulation of molecular fluctuations. Physical Chemistry, Chemical Physics - PCCP 2014 ;Volum 16.(36) s. 19681-19693 <a href="http://dx.doi.org/ 10.1039/c4cp02768j" target="_blank"> http://dx.doi.org/ 10.1039/c4cp02768j </a>
dc.relation.haspartPaper 5: R. Skorpa, T. J. H. Vlugt, D. Bedeaux and S. Kjelstrup. Di_usion of heat and mass in a chemically reactive mixture. Is not included due to copyright.
dc.titleHydrogen dissociation under equilibrium and non-equilibrium conditions A study using molecular dynamicsnb_NO
dc.typeDoctoral thesisnb_NO
dc.subject.nsiVDP::Mathematics and natural science: 400::Chemistry: 440nb_NO


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