Energy Dissipation during Diffusion at Metal Surfaces: Disentangling the   Role of Phonons vs. Electron-Hole Pairs
  Helium spin echo experiments combined with ab initio-based Langevin molecular dynamics simulations are used to quantify the adsorbate-substrate coupling during the thermal diffusion of Na atoms on Cu(111). An analysis of trajectories within the local density friction approximation allows the contribution from electron-hole pair excitations to be separated from the total energy dissipation. Despite the minimal electronic friction coefficient of Na and the relatively small mass mismatch to Cu promoting efficient phononic dissipation, about $(20\pm5)\%$ of the total energy loss is attributable to electronic friction. The results suggest a significant role of electronic non-adiabaticity in the rapid thermalization generally relied upon in adiabatic diffusion theories. 
Simon P. Rittmeyer and David J. Ward and Patrick G\"utlein and John   Ellis and William Allison and Karsten Reuter
cond-mat.mtrl-sci