TDDFT Study of the Charge and Energy Transfer of Ions Interacting with Solid Surfaces

The investigation of processes at the interface between a plasma and a solid surface is of high interest to many different research areas with a vast variety of technical applications. These extend from electronics, surface chemistry and fusion research, to medicine, pharmacy and many more. However, an accurate understanding of the fundamental processes at the plasma-solid interface is often missing. One approach towards a more detailed understanding is to isolate the interaction of atoms, ions, or molecules with the surface and perform scattering experiments. Of special interest are low energy and hyperthermal projectiles with kinetic energies starting in the order of chemical binding energies (in the order of 1 eV) where projectiles are too slow to destroy or sputter the surface but contribute themselves enough energy to cause notable excitations within the electronic system.

In this work, time-dependent density-functional theory (TDDFT) simulations have been employed together with Ehrenfest molecular dynamics (MD) as implemented in the Octopus code to investigate the charge and energy transfer between hyperthermal ions and metal surfaces. The focus of this work lies on the resonant neutralization of protons (H+) interacting with an Al(111) surface. The surface is modeled by a cluster geometry.

Of major importance to TDDFT-MD simulations is the the quality of the approximation applied to the exchange-correlation potential which is investigated and discussed in detail. Also, difficulties connected with the spin-polarization within the calculations are analyzed. Furthermore, the neutralization process is studied, neutralization distances are determined and the energy transfer into electronic, kinetic and phononic degrees of freedom is analyzed.
It has been found that the difference in initial kinetic energy between H+ and H0 projectiles ...



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