Scattering of particles from surfaces is ubiquitous in nature. Understanding the fundamental physics underlying the scattering process is therefore  of great importance. Extensive experimental results for the angular distribution of an Ar atom scattered from a room temperature LiF(100) surface along the [100] and [110] directions were measured almost a decade ago {2}. Most of the attempts to interpret such experiments rely on approximate theories which are fitted successfully to the experimental results via parameters of a simple model potential {3}. In the present work, {1}, we present a different methodology in which the entire potential is based on ab-initio computations without any fitted parameters, and the exact Newtonian equations of motion are solved numerically. In particular, the 3 dimensional ab-initio potential of an Ar atom interacting with a frozen LiF(100) surface was calculated and fitted with a precise functional form. The dissipation of energy to the surface as well as the temperature effect of the surface were attained by coupling the Ar atom to three baths of harmonic modes with friction coefficients which were obtained through on the fly ab-initio computations of the force-force auto correlation function. The resulting angular distributions for Ar atom scattered along either the [100] or [110] directions are in good agreement with the experimental results.

{1} Asaf Azuri and Eli Pollak - to be published.
 
{2} T. Kondo, H. S. Kato, T. Yamada, S. Yamamoto, and M. Kawai, J. Chem, Phys. 122, 244713 (2005).

{3} S. Miret-Artes and E. Pollak, Surf. Sci. Rep. 67, 161 (2012).