Towards TDDFT  for Strongly Correlated Materials

Acharya, Shree Ram; Turkowski, Volodymyr; Rahman, Talat S.

doi:10.3390/computation4030034

Cited by 4 publications

(2 citation statements)

References 65 publications

(74 reference statements)

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“…It is a matter of central importance, for example, in the first-principles simulation of out-of-equilibrium nanoscale functionalities such as dynamical Coulomb blockade 55,56 , and in the firstprinciples spectroscopy of systems comprising transitionmetal ions [57][58][59][60][61][62] . In the realm of non-atomistic calculations, the TDDFT solution of Hubbard type models have also attracted attention [63][64][65][66] , and TDDFT has also been combined with dynamical mean-field theory 67,68 .…”

Section: B Self-interaction Error In the Excited-state Regimementioning

confidence: 99%

TDDFT+$U$: Hubbard corrected approximate density-functional theory in the excited-state regime

Orhan,

O'Regan

2017

Preprint

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We develop a generalization of the Kohn-Sham density functional theory (KS-DFT) + Hubbard U (DFT+U ) method to the excited-state regime. This has the form of Hubbard U corrected linearresponse time-dependent DFT, or 'TDDFT+U '. Combined with calculated linear-response Hubbard U parameters, it may provide a computationally light, first-principles method for the simulation of tightly-bound excitons on transition-metal ions. Our presented implementation combines linearscaling DFT+U and linear-scaling TDDFT, but the approach is broadly applicable. In detailed benchmark tests on two Ni-centred diamagnetic coordination complexes with variable U values, it is shown that the Hubbard U correction to an approximate adiabatic semi-local exchange-correlation interaction kernel lowers the excitation energies of transitions exclusively within the targeted localised subspace, by increasing the exciton binding of the corresponding electron-hole pairs. This partially counteracts the Hubbard U correction to the exchange-correlation potential in KS-DFT, which increases excitation energies into, out of, and within the targeted localised subspace by modifying the underlying KS-DFT eigenspectrum. This compensating effect is most pronounced for optically dark transitions between localized orbitals of the same angular momentum, for which experimental observation may be challenging and theoretical approaches are at their most necessary. Interestingly, we find that first-principles TDDFT+U seems to offer a remarkably good agreement with experiment for a perfectly closed-shell complex on which approximate TDDFT under-performs, but only when TDDFT+U is applied to the DFT eigenspectrum and not to the DFT+U one. In tests on an open-shell, non-centrosymmetric, high-spin cobalt coordination complex, we find that first-principles TDDFT+U again compensates for the DFT+U blue-shift in 3d → 3d transitions, but that using the DFT eigenspectrum is not viable due to the emergence of a singlet instability. Overall, our results point to shortcomings in the contemporary DFT+U corrective potential, either in its functional form, or when applied to transition-metal orbitals but not to ligand ones, or both.

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Section: B Self-interaction Error In the Excited-state Regimementioning

confidence: 99%

TDDFT+$U$: Hubbard corrected approximate density-functional theory in the excited-state regime

Orhan,

O'Regan

2017

Preprint

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show abstract

“…From the work of Acharya et al [19] we can find several details of the recently proposed time-dependent DFT method (for strongly correlated materials), in which the exchange correlation kernel is derived from Dynamical Mean Field Theory (DMFT). The proposed kernels are tested for a one-band Hubbard model and a Mott insulator.…”

Section: Contentmentioning

confidence: 99%