Dielectric embedding GW for weakly coupled molecule-substrate interfaces*

Molecule-substrate interfaces are ubiquitous in many areas of nanoscale materials science. Accurate characterization of their electronic structure from first principles is key in understanding material properties. Although the first-principles GW approach is state-of-the-art and can yield accurate quasiparticle energy levels and interfacial level alignments that are in agreement with experiments, it is computationally challenging for large-scale interfaces. In this work, we develop a dielectric embedding approach based on GW, which significantly reduces the computational cost of direct GW for interfaces without sacrificing accuracy. We perform explicit GW calculations only in the simulation cell containing the molecular adsorbate, in which the dielectric effect of the substrate is effectively embedded. The embedding of the dielectric environment is made possible via a real-space truncation of the Kohn-Sham polarizability. Here, we focus on the interfacial level alignments, i.e., relative positions between molecular frontier orbital resonances and the Fermi level of the substrate, at weakly coupled molecule-substrate interfaces. We demonstrate our approach using a few interfaces of experimental interest.