Non-local potentials for multielectronic atoms interacting with a LiF(001) surface

M. S. GRAVIELLE; J.E. MIRAGLIA

Dresden

Workshop; 22nd. International Workshop on Inelastic Ion-Surface Collisions (IISC); 2017

Local Committee of 22nd IISC

Most of the surface information provided by the method of grazing incidence fast atom diffraction (GIFAD or FAD) crucially relies on the theoretical model used to describe the interaction potential [1]. For insulator surfaces, like LiF, pairwise additive models have shown to provide an appropriate description of the atom-surface interaction, representing a reliable alternative to more complex self-consistent ab-initio calculations [2]. However, the binary atom-ion potentials used within this approach were derived by employing the Local Density Approximation (LDA), which does not include contributions due to non-local electron density terms.In this work we evaluate the interaction between rare gases (closed-shell atoms) - He, Ne, Ar, Kr, and Xe - with fully occupied valence shells, as well as open-shell atoms - N, S, and Cl - with vacancies in the outer level, and a LiF(001) surface within an improved pairwise additive model [3]. The kinetic, exchange and correlation terms of the binary potentials are here evaluated from well-established non-local functionals, while the electron density corresponding to each ionic center of the LiF crystal is obtained from an onion model that takes into account the influence of the Madelung potential. Long-range contributions associated with polarization and van der Waals (vdW) forces, produced by the rearrangement of the atom and surface densities as a result of the mutual interaction, are also included with a similar pairwise additive scheme. The performance of the surface potential model is assessed by contrasting angular positions of rainbow and supernumerary rainbow maxima with available experimental data, finding a good agreement for normal energies in the eV- range.