GW quasi-particle spectra from occupied states only

TL;DR

This paper presents a novel GW approximation method for calculating quasi-particle spectra that avoids using empty states, employing a Lanczos-chain algorithm for efficient computation, validated on benzene and tetraphenylporphyrin.

Contribution

The paper introduces a new approach to GW calculations that eliminates the need for empty state references, improving efficiency for large molecules.

Findings

Accurately computed ionization energies of benzene.

Successfully applied to large molecule tetraphenylporphyrin.

Demonstrated potential for efficient large-scale GW spectra calculations.

Abstract

We introduce a method that allows for the calculation of quasi-particle spectra in the GW approximation, yet avoiding any explicit reference to empty one-electron states. This is achieved by expressing the irreducible polarizability operator and the self-energy operator through a set of linear response equations, which are solved using a Lanczos-chain algorithm. We first validate our approach by calculating the vertical ionization energies of the benzene molecule and then show its potential by addressing the spectrum of a large molecule such as free-base tetraphenylporphyrin.