Excitation energies from ground-state density-functionals by means of generator coordinates

TL;DR

This paper introduces a novel method using generator coordinates within density-functional theory to compute excitation energies from ground-state functionals, offering an alternative to existing excited-state approaches.

Contribution

The paper presents a new approach that incorporates generator coordinates into the Kohn-Sham equations to directly obtain excitation energies from ground-state density functionals.

Findings

Method successfully applied to atoms and ions in He and Li isoelectronic series.

Results compare favorably with time-dependent DFT methods.

Provides a viable alternative for calculating excited states in DFT.

Abstract

The generator-coordinate method is a flexible and powerful reformulation of the variational principle. Here we show that by introducing a generator coordinate in the Kohn-Sham equation of density-functional theory, excitation energies can be obtained from ground-state density functionals. As a viability test, the method is applied to ground-state energies and various types of excited-state energies of atoms and ions from the He and the Li isoelectronic series. Results are compared to a variety of alternative DFT-based approaches to excited states, in particular time-dependent density-functional theory with exact and approximate potentials.