Wannier interpolation of one-particle Green's functions from coupled-cluster singles and doubles (CCSD)

TL;DR

This paper introduces two Wannier-based interpolation schemes for one-particle Green's functions derived from CCSD calculations in periodic systems, improving computational efficiency and physical accuracy.

Contribution

It presents novel Wannier interpolation methods for CCSD Green's functions, including direct and self-energy-mediated schemes, with detailed validation on molecular chains.

Findings

Self-energy-mediated interpolation yields more physically accurate GFs.

Direct interpolation suffers from numerical artifacts due to slow convergence.

Schemes are applicable to other correlated methods providing GFs.

Abstract

We propose two schemes for interpolation of the one-particle Green's function (GF) calculated within coupled-cluster singles and doubles (CCSD) method for a periodic system. They use Wannier orbitals for circumventing huge cost for a large number of sampled k points. One of the schemes is the direct interpolation, which obtains the GF straightforwardly by using Fourier transformation. The other is the self-energy-mediated interpolation, which obtains the GF via the Dyson equation. We apply the schemes to a LiH chain and trans-polyacetylene and examine their validity in detail. It is demonstrated that the direct-interpolated GFs suffer from numerical artifacts stemming from slow convergence of CCSD GFs in real space, while the self-energy-mediated interpolation provides more physically appropriate GFs due to the localized nature of CCSD self-energies. Our schemes are also applicable to other explicitly correlated methods capable of providing GFs.