Quasiparticle spectra from a non-empirical optimally-tuned range-separated hybrid density functional

TL;DR

This paper introduces a non-empirical, system-specific range-separated hybrid density functional method to accurately compute quasiparticle energies, offering a computationally cheaper alternative to GW for large molecules.

Contribution

The paper develops a novel non-empirical tuning approach for range-separated hybrid functionals to accurately predict quasiparticle spectra, comparable to GW calculations.

Findings

Accurately predicts quasiparticle energies for benchmark organic molecules.

Demonstrates comparable accuracy to GW approximation.

Provides a computationally inexpensive alternative for large systems.

Abstract

We present a method for obtaining outer valence quasiparticle excitation energies from a DFT-based calculation, with accuracy that is comparable to that of many-body perturbation theory within the GW approximation. The approach uses a range-separated hybrid density functional, with asymptotically exact and short-range fractional Fock exchange. The functional contains two parameters - the range separation and the short-range Fock fraction. Both are determined non-empirically, per system, based on satisfaction of exact physical constraints for the ionization potential and many-electron self-interaction, respectively. The accuracy of the method is demonstrated on four important benchmark organic molecules: perylene, pentacene, 3,4,9,10-perylene-tetracarboxylic-dianydride (PTCDA) and 1,4,5,8-naphthalene-tetracarboxylic dianhydride (NTCDA). We envision that for finite systems the approach could provide an inexpensive alternative to GW, opening the door to the study of presently out of reach large-scale systems.