ReaxFF MgH reactive force field for magnesium hydride systems

Sam Cheung, Wei Qiao Deng, Adri C.T. Van Duin, William A. Goddard

Research output: Contribution to journalArticle

200 Scopus citations

Abstract

We have developed a reactive force field (ReaxFF MgH) for magnesium and magnesium hydride systems. The parameters for this force field were derived from fitting to quantum chemical (QM) data on magnesium clusters and on the equations of states for condensed phases of magnesium metal and magnesium hydride crystal. The force field reproduces the QM-derived cell parameters, density, and the equations of state for various pure Mg and MgH 2 crystal phases as well as and bond dissociation, angle bending, charge distribution, and reaction energy data for small magnesium hydride clusters. To demonstrate one application of ReaxFF MgH, we have carried out MD simulations on the hydrogen absorption/desorption process in magnesium hydrides, focusing particularly on the size effect of MgH: nanoparticles on H 2 desorption kinetics. Our results show a clear relationship between grain size and heat of formation of MgH 2; as the particle size decreases, the heat of formation increases. Between 0.6 and 2.0 run, the heat of formation ranges from -16 to -19 kcal/Mg and diverges toward that of the bulk value (-20.00 kcal/Mg) as the particle diameter increases beyond 2 nm. Therefore, it is not surprising to find that Mg nanoparticles formed by ball milling (20-100 nm) do not exhibit any significant change in thermochemical properties.

Original languageEnglish (US)
Pages (from-to)851-859
Number of pages9
JournalJournal of Physical Chemistry A
Volume109
Issue number5
DOIs
StatePublished - Feb 10 2005

All Science Journal Classification (ASJC) codes

  • Physical and Theoretical Chemistry

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