Ojwang, J. G. O. and van Santen, Rutger and Kramer, Gert Jan and van Duin, Adri C. T. and Goddard, William A., III (2008) Modeling the sorption dynamics of NaH using a reactive force field. Journal of Chemical Physics, 128 (16). Art. No. 164714. ISSN 0021-9606 http://resolver.caltech.edu/CaltechAUTHORS:OJGjcp08
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We have parametrized a reactive force field for NaH, ReaxFFNaH, against a training set of ab initio derived data. To ascertain that ReaxFFNaH is properly parametrized, a comparison between ab initio heats of formation of small representative NaH clusters with ReaxFFNaH was done. The results and trend of ReaxFFNaH are found to be consistent with ab initio values. Further validation includes comparing the equations of state of condensed phases of Na and NaH as calculated from ab initio and ReaxFFNaH. There is a good match between the two results, showing that ReaxFFNaH is correctly parametrized by the ab initio training set. ReaxFFNaH has been used to study the dynamics of hydrogen desorption in NaH particles. We find that ReaxFFNaH properly describes the surface molecular hydrogen charge transfer during the abstraction process. Results on heat of desorption versus cluster size shows that there is a strong dependence on the heat of desorption on the particle size, which implies that nanostructuring enhances desorption process. To gain more insight into the structural transformations of NaH during thermal decomposition, we performed a heating run in a molecular dynamics simulation. These runs exhibit a series of drops in potential energy, associated with cluster fragmentation and desorption of molecular hydrogen. This is consistent with experimental evidence that NaH dissociates at its melting point into smaller fragments.
|Additional Information:||©2008 American Institute of Physics. Received 12 December 2007; accepted 17 March 2008; published 28 April 2008. This work is part of the research programs of Advanced Chemical Technologies for Sustainability (ACTS), which is funded by Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO).|
|Subject Keywords:||ab initio calculations, charge exchange, desorption, dissociation, equations of state, heat of formation, hydrogen, melting point, molecular dynamics method, particle size, potential energy surfaces, pyrolysis, sodium compounds|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Archive Administrator|
|Deposited On:||30 Apr 2008|
|Last Modified:||26 Dec 2012 09:59|
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