The dynamics of the H + D/Si(001) reaction: a trajectory study based on ab initio potentials

The adiabatic potential energy surface for the reaction of H atoms with the deuterated Si(001) surface is calculated using a slab geometry and spin-polarized density functional theory with gradient corrections. Its dynamical implications are investigated through classical trajectory simulations. A significant probability for the exothermic production of HD molecules is found. In agreement with recent experiments, the kinetic energy of the HD molecules is the most important channel of energy disposal. For larger energies of incidence of the H atoms, molecular and substrate degrees of freedom take up an increasing amount of energy, leading to a broadening of the HD kinetic energy distributions.