Photoionization and core resonances from range-separated density-functional theory: General formalism and example of the beryllium atom

TL;DR

This paper evaluates the effectiveness of range-separated TDDFT methods, specifically TDRSH and TDLRSH, in calculating photoionization spectra and core resonances of the beryllium atom, showing significant improvements over traditional methods.

Contribution

It introduces and compares two variants of range-separated TDDFT for photoionization spectra, demonstrating their advantages over standard approaches.

Findings

TDRSH and TDLRSH significantly improve spectral accuracy over TDLDA.

Both methods outperform TDLDA in describing core resonances.

Range-separated TDDFT offers a promising approach for photoionization studies.

Abstract

We explore the merits of linear-response range-separated time-dependent density-functional theory (TDDFT) for the calculation of photoionization spectra. We consider two variants of range-separated TDDFT, namely the timedependent range-separated hybrid (TDRSH) scheme which uses a global range-separation parameter and the timedependent locally range-separated hybrid (TDLRSH) which uses a local range-separation parameter, and compare with standard time-dependent local-density approximation (TDLDA) and time-dependent Hartree-Fock (TDHF). We show how to calculate photoionization spectra with these methods using the Sternheimer approach formulated in a nonorthogonal B-spline basis set with appropriate frequency-dependent boundary conditions. We illustrate these methods on the photoionization spectrum of the Be atom, focusing in particular on the core resonances. Both the TDRSH and TDLRSH photoionization spectra are found to constitute a large improvement over the TDLDA photoionization spectrum and a more modest improvement over the TDHF photoionization spectrum.