Dissipative friction dynamics within the density-functional based tight-binding scheme

The accurate description of an atom or molecule colliding with a metal surface remains challenging. Several strategies have been performed over the past decades to include in a Langevin dynamics the energy transfer related to electron–hole pair excitations in a phenomenological way through a friction contribution. We report the adaptation of two schemes previously developed in the literature to couple the electronic friction dynamics with the density-functional based tight-binding (DFTB) approach. The first scheme relies on an electronic isotropic friction coefficient determined from the local electronic density (local density friction approximation or LDFA). In the second one, a tensorial friction is generated from the non-adiabatic couplings of the ground electronic state with the single electron–hole excitations (electron tensor friction approximation or ETFA). New DFTB parameterization provides potential energy curves in good agreement with first-principle density-functional theory (DFT) energy calculations for selected pathways of hydrogen atom adsorbing onto the (100) silver surface or penetrating subsurface. Preliminary DFTB/Langevin dynamics simulations are presented for hydrogen atom scattering from the (100) silver surface and energy loss timescales are characterized.