Van der Waals effects on grazing incidence fast atom diffraction for H/LiF(001)

TL;DR

This study models grazing incidence fast atom diffraction of hydrogen on LiF(001), demonstrating that Van der Waals interactions significantly improve the match between simulations and experiments at low energies.

Contribution

It introduces a combined DFT and semi-quantum model to analyze Van der Waals effects in GIFAD, highlighting their importance in low-energy regimes.

Findings

Van der Waals interactions improve simulation accuracy at energies below 0.5 eV

Better agreement between theory and experiment when including Van der Waals effects

Van der Waals effects are significant in low-to-intermediate energy GIFAD regimes

Abstract

We theoretically address grazing incidence fast atom diffraction (GIFAD) for H atoms impinging on a LiF(001) surface. Our model combines a description of the H-LiF(001) interaction obtained from Density Functional Theory calculations with a semi-quantum treatment of the dynamics. We analyze simulated diffraction patterns in terms of the incidence channel, the impact energy associated with the motion normal to the surface, and the relevance of Van der Waals (VdW) interactions. We then contrast our simulations with experimental patterns for different incidence conditions. Our most important finding is that, for normal energies lower than 0.5 eV and incidence along the <100> channel, the inclusion of Van der Waals interactions in our potential energy surface yields a greatly improved accord between simulations and experiments. This agreement strongly suggests a non-negligible role of Van der Waals interactions in H/LiF(001) GIFAD in the low-to-intermediate normal energy regime.