Time-dependent density-functional molecular-dynamics study of the isotope effect in chemicurrents

The energy dissipation into electron-hole pairs has been simulated ab initio within time-dependent density-functional theory for spin-unpolarized hydrogen atoms interacting with the Al on-top site at the Al(1 1 1) surface. The electron-hole pair excitation spectra are characterized by an approximately exponentially decaying tail of the electron energy distribution. It is shown that both the energy dissipated into electron-hole pairs and the excitation spectra, and hence the chemicurrent yield, show an isotope dependence identical to what expected from the linear friction ansatz and the forced oscillator model.