Electronic energy level alignment at metal-molecule interfaces with a GW approach

TL;DR

This paper uses GW calculations to accurately predict the electronic energy level alignment at a metal-molecule interface, improving agreement with experimental photoemission data.

Contribution

It demonstrates that refined GW self-energy calculations can correct previous underestimations of molecular energy levels at interfaces, achieving quantitative agreement with experiments.

Findings

G0W0 underestimates molecular resonance energies by up to 0.8 eV

Adjustments to GW self-energy improve agreement with photoemission data

Refined GW approach accurately predicts interfacial energy level alignment

Abstract

Using density functional theory and many-body perturbation theory within a GW approximation, we calculate the electronic structure of a metal-molecule interface consisting of benzene diamine (BDA) adsorbed on Au(111). Through direct comparison with photoemission data, we show that a conventional G$_0$W$_0$ approach can underestimate the energy of the adsorbed molecular resonance relative to the Au Fermi level by up to 0.8 eV. The source of this discrepancy is twofold: a 0.7 eV underestimate of the gas phase ionization energy (IE), and a 0.2 eV overestimate of the Au work function. Refinements to self-energy calculations within the GW framework that account for deviations in both the Au work function and BDA gas-phase IE can result in an interfacial electronic level alignment in quantitative agreement with experiment.