Assessing the performance of ΔSCF and the diagonal second-order self-energy approximation for calculating vertical core excitation energies

Zamani, Abdulrahman Y.; Hratchian, Hrant P.

doi:10.1063/5.0100638

Cited by 2 publications

(1 citation statement)

References 91 publications

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“…First of all, these methods do not include spin coupling, so there is no distinction between singlet and triplet excitations starting from a singlet ground state. The singlet–triplet excitation gap for c → υ excitation could be estimated as , E singlet − E triplet ≈ 2 [ false( c υ false| c υ false) − false( c c false| υ υ false) ] If one is willing to introduce two-electron integrals, then one may also correct the ΔSCF result via perturbation theory. − However, direct use of electron repulsion integrals is a step away from the purpose of using eigenvalue-based methods in the first place. As such, we will not attempt to compute any spin couplings in the present work.…”

Section: Theoretical Methodsmentioning

confidence: 99%

Fractional-Electron and Transition-Potential Methods for Core-to-Valence Excitation Energies Using Density Functional Theory

Jana

Herbert

2023

J. Chem. Theory Comput.

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Methods for computing X-ray absorption spectra based on a constrained core hole (possibly containing a fractional electron) are examined. These methods are based on Slater's transition concept and its generalizations, wherein core-to-valence excitation energies are determined using Kohn−Sham orbital energies. Methods examined here avoid promoting electrons beyond the lowest unoccupied molecular orbital, facilitating robust convergence. Variants of these ideas are systematically tested, revealing a best-case accuracy of 0.3−0.4 eV (with respect to experiment) for K-edge transition energies. Absolute errors are much larger for higher-lying near-edge transitions but can be reduced below 1 eV by introducing an empirical shift based on a charge-neutral transition-potential method, in conjunction with functionals such as SCAN, SCAN0, or B3LYP. This procedure affords an entire excitation spectrum from a single fractional-electron calculation, at the cost of ground-state density functional theory and without the need for state-by-state calculations. This shifted transition-potential approach may be especially useful for simulating transient spectroscopies or in complex systems where excitedstate Kohn−Sham calculations are challenging. = c c(1) are estimated as differences between final-state (virtual) energy levels ε υ and the initial-state (core) level ε c . In some cases, a fractional electron may be placed into the lowest unoccupied molecular orbital (LUMO), as described in Section 2, but not into any higher-lying virtual MO. Transition intensities are computed according to

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Section: Theoretical Methodsmentioning

confidence: 99%

Fractional-Electron and Transition-Potential Methods for Core-to-Valence Excitation Energies Using Density Functional Theory

Jana

Herbert

2023

J. Chem. Theory Comput.

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Long-range Corrected Density Functional Theory Including a Two-Gaussian Hartree−Fock Operator for High Accuracy Core-excitation Energy Calculations of Both the Second- and Third-Row Atoms (LC2gau-core-BOP)

Ahn,

Nakajima,

Hirao

et al. 2024

J. Chem. Theory Comput.

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In the previous work, LCgau-core-BOP, which includes the short-range interelectronic Gaussian attenuating Hartree−Fock (HF) exchange to the long-range HF exchange, showed high accuracy core-excitation energies from 1s orbitals of the second-row atoms (1s → π*, 1s → σ*, 1s → n*, and 1s → Rydberg), but underestimates the core-excitation energies from 1s orbitals of the third-row atoms. To improve this, we added one more Gaussian attenuating HF exchange to LCgau-core-BOP. We named it LC2gau-core-BOP, which achieves a mean absolute error (MAE) of 0.6 and 0.3 eV for core excitation energies of the second-and third-row atoms of the tested small molecules, respectively. We found that the inclusion of the short-range interelectronic HF exchange at a distance ranging from 0.2 to 0.6 a.u. contributes to the increase of performances on 1s orbital energy calculations of the second-row atoms, while the inclusion of more short-range interelectronic HF exchange at a distance ranging from 0 to 0.2 a.u. does to the increase of performance on 1s orbital energy calculations of the third-row atoms. It is notable that all of these improvements were accomplished using flexible Gaussian attenuating HF exchange inclusion. LC2gau-core-BOP shows deviations of less than 0.8 eV from experimental values for all of the core-excitation energies of the tested medium-size molecules consisting of thymine, oxazole, glycine, and dibenzothiophene sulfone. Moreover, by optimizing one parameter of the OP correlation functional, LC2gau-core-BOP provides atomization energies over the G3 test set with an accuracy comparable to that of B3LYP.

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Assessing the performance of ΔSCF and the diagonal second-order self-energy approximation for calculating vertical core excitation energies

Cited by 2 publications

References 91 publications

Fractional-Electron and Transition-Potential Methods for Core-to-Valence Excitation Energies Using Density Functional Theory

Fractional-Electron and Transition-Potential Methods for Core-to-Valence Excitation Energies Using Density Functional Theory

Long-range Corrected Density Functional Theory Including a Two-Gaussian Hartree−Fock Operator for High Accuracy Core-excitation Energy Calculations of Both the Second- and Third-Row Atoms (LC2gau-core-BOP)

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