Energy-Specific Linear Response TDHF/TDDFT for Calculating High-Energy Excited States

Abstract

An energy-specific TDHF/TDDFT method is introduced in this article for excited state calculations. This approach extends the conventional TDHF/TDDFT implementation to obtain excited states above a predefined energy threshold. The method introduced and developed in this work enables computationally efficient yet rigorous calculations of energy-specific spectra, e.g., X-ray absorption involving extremely high-energy transitions. All transitions are solved in the full molecular orbital space, and orthogonality to the ground state and lower-lying excited states is preserved for each high-energy excited state. Encouraging computational savings are observed in calculating the targeted energy spectrum, while the transition energies, as well as oscillator strengths, remain identical to the results from the standard implementation.

Communication: X-ray absorption spectra and core-ionization potentials within a core-valence separated coupled cluster framework

“…also been presented in recent years. [25][26][27] To the best of our knowledge, this is the first study exploring the applicability of the CVS approximation at the CC level of theory. We note nonetheless a very recent study by Peng et al 9 where an alternative, and much more elaborate, approach to target core excitation energies within the equation-of-motion coupled cluster singles and doubles (EOM-CCSD) ansatz is presented.…”

Quantum confinement effects on optical transitions in nanodiamonds containing nitrogen vacancies

“…51 The ground state electronic structures were obtained by solving the Kohn-Sham equation using the hybrid B3LYP functional. [52][53][54] We also compared the optical spectra computed using the long-range corrected (LC-) version 57-59 and its energy specific implementation for the high energy states 60,61 . Diffuse functions have been previously shown to be unimportant for clusters whose diameter is larger than 1 nm 39 .…”

Core and valence excitations in resonant X-ray spectroscopy using restricted excitation window time-dependent density functional theory

“…68,69 Li et al also suggested to project the TDDFT response equation into a subspace, in which the trial vectors correspond to energies in a specific range. 70 Conventional density functionals used in TDDFT calculations often underestimate core excitation energies, which is due to the self-interaction error. 61,[71][72][73][74] Core-valence hybrid 71,75,76 and short-range corrected hybrid functionals 77,78 were proposed to improve the accuracy of TDDFT for core excitations.…”

“…This conclusion is based on several successful applications of the REW-TDDFT approach in conjunction with using non-local hybrid density functionals on molecular systems. 62,66,70,78,80 Frequency-dependent exchange-correlation kernels have been proposed recently and tested on model systems. 81,82 …”