Unraveling the variational breakdown of core valence separation calculations: Diagnostic and cure to the over relaxation error of double core hole states

Anthony Ferté (1, 2) , Emmanuel Giner (3) , Richard Taïeb (1) , Stéphane Carniato (1)

1 LCPMR - Laboratoire de Chimie Physique - Matière et Rayonnement
2 CEISAM - Chimie Et Interdisciplinarité : Synthèse, Analyse, Modélisation
3 LCT - Laboratoire de chimie théorique

The core valence separation (CVS) approximation is the most employed strategy to prevent the variational collapse of standard wave function optimization when attempting to compute electronic states bearing one or more electronic vacancies in core orbitals. Here, we explore the spurious consequences of this approximation on the properties of the computed core hole states. We especially focus on the less studied case of double core hole (DCH) states, whose spectroscopic interest has recently been rapidly growing. We show that the CVS error leads to a systematic underestimation of DCH energies, a property in stark contrast with the case of single core hole states. We highlight that the CVS error can then be interpreted as an over relaxation effect and design a new correction strategy adapted to these specificities.

Keywords: core hole state; core valence separation; variational correction; electronic structure method; Export Citation CrossMark

Domains: Theoretical and/or physical chemistry

Anthony Ferté, Emmanuel Giner, Richard Taïeb, Stéphane Carniato. Unraveling the variational breakdown of core valence separation calculations: Diagnostic and cure to the over relaxation error of double core hole states. The Journal of Chemical Physics, 2023, 159 (14), pp.144104. ⟨10.1063/5.0159493⟩. ⟨hal-04295351⟩