ISSN:
1089-7690
Source:
AIP Digital Archive
Topics:
Physics
,
Chemistry and Pharmacology
Notes:
The unimolecular decomposition dynamics of Si2H4 have been investigated using classical trajectory methods on a global potential-energy surface fitted to the results of ab initio calculations and the available experimental data. The required phase-space averages are computed using Metropolis sampling techniques. It is found that unless the parameters of the Markov walk are adjusted for each different type of atom present, extremely long Markov walks are required to adequately cover the phase space of the system. Microcanonical rate coefficients for the decomposition of Si2H4 into all open channels are reported at energies in the range 5.0〈E〈9.0 eV. The most important dissociation channel over this energy range is three-center elimination of molecular hydrogen leading to H2 Si=Si. At energies below 7.0 eV, the other channels are, in order of importance, Si–Si bond rupture, four-center H2 elimination, and simple Si–H bond rupture. At or above 8.0 eV, four-center H2 elimination replaces Si–Si bond rupture as the second most important decomposition channel. The energy dependence of the rate coefficients is well described by an RRK expression. Three-center H2 elimination involves a simultaneous rupture of both Si–H bonds whereas the four-center elimination is found to proceed by a hydrogen atom transfer process followed by H2 elimination. Except for a small propensity to form H2 with excess rotational energy, the energy partitioning among the products is nearly statistical. A comparison study of the decomposition of Si2H4 complexes formed by the recombination of two SiH2 molecules shows that the rates for both three- and four-center H2 elimination are in agreement with those computed using a statistical distribution of the same internal energy. The rate for Si–Si bond rupture, however, is significantly larger for Si2H4 complexes formed by SiH2 recombination than for Si2H4 molecules with the same internal energy randomly distributed. The decomposition dynamics of SiH2 on the global surface are also reported.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.455197
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