Screening in 2D: GW calculations for surfaces and thin films using the repeated-slab approach

TL;DR

This paper critically examines the repeated-slab approach for GW calculations of surfaces and thin films, identifying key differences from bulk screening and proposing correction schemes for improved accuracy.

Contribution

It provides a detailed analysis of long-range screening effects in 2D systems and introduces correction methods to enhance GW calculations for surfaces and thin films.

Findings

Quantified the impact of anisotropic screening on GW results.

Developed correction schemes for slab-slab interactions.

Demonstrated improved accuracy in GW calculations for silicon and NaCl thin films.

Abstract

In the context of photoelectron spectroscopy, the $GW$ approach has developed into the method of choice for computing excitation spectra of weakly correlated bulk systems and their surfaces. To employ the established computational schemes that have been developed for three-dimensional crystals, two-dimensional systems are typically treated in the repeated-slab approach. In this work we critically examine this approach and identify three important aspects for which the treatment of long-range screening in two dimensions differs from the bulk: (1) anisotropy of the macroscopic screening (2) $\mathbf k$-point sampling parallel to the surface (3) periodic repetition and slab-slab interaction. For prototypical semiconductor (silicon) and ionic (NaCl) thin films we quantify the individual contributions of points (1) to (3) and develop robust and efficient correction schemes derived from the classic theory of dielectric screening.