title: Electron affinities and ionisation potentials for atoms via "benchmark" tdDFT calculations with and without exchange kernels.
abstract: One of the known weaknesses of the adiabatic connection fluctuation dissipation (ACFD) correlation energy functional under the direct random-phase approximation (RPA) is its failure to accurately predict energy differences between dissimilar systems. In this work we evaluate ionisation potentials I and electron affinities A for atoms and ions with one to eighteen electrons using the ACFD functional under the RPA, and with the "PGG (Petersilka-Gossmann-Gross)" and "RXH (radial exchange hole)" model exchange kernels. All calculations are carried out using a real-space, all electron method with an exact exchange groundstate to minimise errors. As expected, the RPA is less accurate even than some regular density functional theory approaches, while the introduction of a dynamical exchange kernel improves results. In contrast to the case of atomic groundstate energies, the PGG kernel outperforms the RXH kernel for I and A. Mean absolute errors for I/A are found to be 3.27/2.38 kcal/mol, 4.38/5.43 kcal/mol, and 9.24/ 8.94 kcal/mol for the PGG, RXH, and RPA, respectively. We thus show that the inclusion of even the simple "RXH" kernel improves both quantities when compared to the RPA.
authors.affiliation: Queensland Micro- and Nanotechnology Centre, Griffith University, Nathan, Queensland 4111, Australia.
authors.forename: Tim
authors.initials: T
authors.lastname: Gould
authors.forename: John F
authors.initials: JF
authors.lastname: Dobson