On the accuracy of first-principles lateral interactions: Oxygen at Pd(100)

TL;DR

This study uses a first-principles lattice-gas Hamiltonian approach to accurately determine oxygen lateral interactions on Pd(100), revealing the importance of many-body effects and uncertainties in modeling surface ordering.

Contribution

It provides a detailed analysis of lateral interactions and their uncertainties, highlighting the limitations of pairwise approximations in surface adsorption modeling.

Findings

Quantitative agreement with experimental ordering behavior.

Uncertainties mainly affect on-site energy and transition temperatures.

Pairwise interaction assumption introduces significant spurious contributions.

Abstract

We employ a first-principles lattice-gas Hamiltonian (LGH) approach to determine the lateral interactions between O atoms adsorbed on the Pd(100) surface. With these interactions we obtain an ordering behavior at low coverage that is in quantitative agreement with experimental data. Uncertainties in the approach arise from the finite LGH expansion and from the approximate exchange-correlation (xc) functional underlying the employed density-functional theory energetics. We carefully scrutinize these uncertainties and conclude that they primarily affect the on-site energy, which rationalizes the agreement with the experimental critical temperatures for the order-disorder transition. We also investigate the validity of the frequently applied assumption that the ordering energies can be represented by a sum of pair terms. Restricting our LGH expansion to just pairwise lateral interactions, we find that this results in effective interactions which contain spurious contributions that are of equal size, if not larger than any of the uncertainties e.g. due to the approximate xc functional.