  To understand the recently observed mysterious non-adiabatic energy transfer
for hyperthermal H atom scattering from a semiconductor surface, Ge(111)c(2*8),
we present a mixed quantum-classical non-adiabatic molecular dynamics model
based on time-dependent evolution of Kohn-Sham orbitals and a classical path
approximation. Our results suggest that facile non-adiabatic transitions occur
selectively at the rest atom site, featuring excitation of valance band
electrons to the conduction band, but not at the adatom site. This drastic site
specificity can be attributed to the changes of the local band structure upon
energetic H collisions at different surface sites, leading to transient
near-degeneracies and significant couplings between occupied and unoccupied
orbitals at the rest atom, but not at the adatom. These insights shed valuable
light on the collisional induced non-adiabatic dynamics at semiconductor
surfaces.
