Trajectory study of the formation and decay of silicon trimer complexes in monomer–dimer collisions

Abstract

The dynamics of the formation and dissociation of Si3 complexes in atom–dimer collisions have been investigated using quasiclassical trajectories on a potential-energy surface that is a global fit to the available experimental data and ab initio CI and MP4 results. The fitted surface yields excellent results for the equilibrium geometries of both Si2 and Si3. The rms deviation of the energies from the MP4 calculations is 0.117 eV. The Si3 fundamental frequencies agree with the MP4 results to within 37 cm−1 or less. Formation cross sections for Si3 formation are reported as a function of initial relative translational energy. These cross sections are found to exhibit a near double exponential dependence upon relative translational energy. The thermal rate coefficients are on the order of 1015 cm3/mol s and show a negative temperature dependence at temperatures below 200 K. Microcanonical dissociation rate coefficients for Si3 complexes are reported for six different internal Si3 energies. These values follow an RRK energy dependence with s=2.67. The average Si3 lifetimes are found to lie in the range 4.71×10−13−5.02×10−11 s.