GIFAD for light atoms on insulating surfaces. The role of van der Waals interactions

M.S. GRAVIELLE; G. A. BOCAN; J.D. FUHR

Dresden

Workshop; 22nd International Workshop on Inelastic Ion-Surface Collisions; 2017

IISC

Grazing incidence fast atom diffraction (GIFAD) is an extraordinarilysensitive phenomenon. It was first reported in 2007 [1, 2] and has sincebecome a powerful surface analysis technique as well as a most useful tool for testing potential energy surfaces (PESs).In this work we theoretically address GIFAD for light atoms on insulatingalkali-halide surfaces. Our model combines a description of the projectile-surface interaction by means of a three-dimensional PES, built from high-precision density functional theory (DFT) calculations; with a semiquantum treatment of the elastic scattering process within the surface initial-value representation (SIVR) [3].The focus of our discussion is the role of van der Waals (vdW) interactions and how they affect the diffraction patterns. In a recent article we reported marked vdW effects on GIFAD for H/LiF(001), provided there be no polarization effects along the incidence channel and the perpendicular energy be low enough for reflection to take place at regions relatively far from the surface [4]. In the present study we further discuss those results and extend the analysis to similar systems, particularly 3 He/KCl(001), 4 He/KCl(001) and H/KCl(001).The visibility of vdW interactions through their effect on GIFAD patternspositions this highly sensitive technique as a promising tool for comparing the different approaches to vdW within DFT, and thus for developing more accurate descriptions of these interactions.