Exchange-correlation holes in metal surfaces using nonlocal density-functional theory

We apply the fully nonlocal weighted density approximation (WDA) to calculate the electronic structure of surfaces in order to investigate the nonlocal nature of interactions between a surface and adatoms or molecules. In particular, exchange-correlation holes are calculated for the jellium and Cu(100) surfaces. We show that the exchange-correlation hole differs significantly from that found in the local density approximation. In addition, we find that there are substantial nonlocal effects predicted for Cu(100), which therefore shed doubt on the accuracy of density-functional surface calculations using the standard (semi-)local functionals. Our results suggest that the WDA can offer useful improvement in predictions of the behavior of surfaces over (semi-)local functional forms.