DFT calculations of correlation energies for excited electronic states using MCSCF wave functions

Abstract

ABSTRACT:A large set of correlation energy functionals has been applied, in a post-SCF procedure, to incorporate the correlation energy of several excited atomic states using MCSCF wave functions. The results show that the application of standard density functionals does not consider the double count of the correlation energy obtained by the MCSCF wave function. However, the use of some dependence on the two-body density matrix improves the results, with a partial account of this correlation energy balance.

Loads of special authorship functions: Linear growth in the percentage of “equal first authors” and corresponding authors

“…In contrast, a practical MR‐DFT computational scheme is based on the modified universal functional F p [ρ( r )] of “wave function‐driven” MR‐DFT 9–26, 28, 40–47 given in Eq. (5): F p [ρ( r )] is defined by limiting a variational space to a specific extent of a wave function expansion.…”

“…But up to now, any XC functional for the spin symmetry‐adapted KS‐DFT method, by which we can describe the static correlation correctly, has remained unknown. Instead, a straightforward remedy for the case is to introduce the MR wave function into the DFT 9–47. (The CI‐DFT equation presented in Ref.…”

“…Two new directions i.e., MR‐DFT 9–47 and KS‐DFT with the OEP method 48, 49, 52–62 in DFT are developed for these purposes. MR‐DFT using the Coulomb division method 27, 29–38, 45, 46 can be applied for any combination of wave function and DFT xc functional.…”

Understanding of the Switching Mechanism of a Pt/Ni-Doped SrTiO3 Junction via Current–Voltage and Capacitance–Voltage Measurements

“…Despite all these problems, a variety of promising and appealing formalisms have been proposed in the past years and this continues to remain a very fertile and demanding area of research. Some of the notable ones are, for example, (a) the subspace formulation of DFT [55] invoking the concept of ensemble density instead of the pure-state density, (b) a constrained search method [56] bypassing the Hohenberg-Kohn theorem while defining the functionals in terms of the Slater determinants, (c) several variants of the ensemble density approach [57,58] employing several different forms of the approximate functionals, (d) a Rayleigh-Ritz-type variational principle of unequally weighted ensemble [59], (e) a time-dependent (TD) formulation of DFT for excited states [60][61][62], based on the TD density functional response theory, (f) a perturbative treatment [63,64], where the non-interacting KS Hamiltonian corresponds to the zeroth-order Hamiltonian and the differences in the KS eigenvalues simply give the zerothorder excitation energies. Recently, multiplet energies for transition metal atoms and ions with 3d n configurations have been reported [65] using the SCF KS orbitals to construct the atomic multiplet determinantal combinations.…”

CASSCF version of density functional theory

“…Some spin‐projection approaches following UKS‐DFT (PUKS‐DFT) 4, 7–9 are available for these cases, but it is known that the projection‐after variation approach of PUKS‐DFT leads to a spurious cusp in the computed potential curve 8, as in the case of HF theory 10. Multireference (MR) density functional theory (DFT) enables us to handle the issue 11–41. An important class of MR‐DFT is complete‐active‐space (CAS)‐DFT, where the CAS wave function is employed to treat resonating features completely.…”