The performance of time-dependent density functional theory based on a noncollinear exchange-correlation potential in the calculations of excitation energies

Abstract

In the present work we have studied the accuracy of excitation energies calculated from spin-flip transitions with a formulation of time-dependent density functional theory based on a noncollinear exchange-correlation potential proposed in a previous study. We compared the doublet-doublet excitation energies from spin-flip transitions and ordinary transitions, calculated the multiplets splitting of some atoms, the singlet-triplet gaps of some diradicals, the energies of excited quartet states with a doublet ground state. In addition, we attempted to calculate transition energies with excited states as reference. We compared the triplet excitation energies and singlet-triplet separations of the excited state from spin-flip and ordinary transitions. As an application, we show that using excited quartet state as reference can help us fully resolve excited states spin multiplets. In total the obtained excitation energies calculated from spin-flip transitions agree quite well with other theoretical results or experimental data.

Ligand field density functional theory calculation of the 4f2 → 4f15d1 transitions in the quantum cutter Cs2KYF6:Pr3+

“…13 a Department of Chemistry of the University of Fribourg, Chemin du Musée 9, DFT can in principle be used to calculate optical properties of materials, [14][15][16] e.g. using TDDFT 17,18 or Delta-SCF. 19,20 However, combining classical ligand field theory 21,22 or, in a certain context, crystal field theory with DFT gives rise to interesting results with a relatively good agreement with the experimental data.…”

Singlet-triplet gaps in large multireference systems: Spin-flip-driven alternatives for bioinorganic modeling

“…Initially developed within the SCF or the CIS͑D͒ frameworks, 50,51 the SF approach has been merged with DFT through time-dependent density functional theory within the Tamm-Dancoff approximation, [54][55][56] a procedure that has been successfully applied to the description of ͑poly͒radicals, 54,56,63 and to that of some transition-metal compounds. [64][65][66] A detailed discussion of the differences occurring between TD-DFT and SF-͑TD͒DFT can be found in Refs.…”

The behavior of active diffusiophoretic suspensions: An accelerated Laplacian dynamics study

“…The scheme, called configuration-interaction-corrected TammDancoff approximation (CIC-TDA), 389 gives the correct dimensionality of conical intersections while giving energies similar to TDDFT-TDA away from conical intersections. The dressed TDDFT [390][391][392][393] and spin-flip TDDFT [394][395][396][397] methods also have the correct dimensionality due to the inclusion of doubly excited configurations, as discussed below.…”

“…The problem can also be remedied in a different way by spin-flip TDDFT. [394][395][396][397] Spin-flip TDDFT uses a triplet state as the reference state to which single excitations with spin flip are applied, resulting in both singly excited and doubly excited configurations relative to a closed-shell ground state. It can produce accurate excitation energies when used with the noncollinear kernel and some functionals, but there can be problems from spin contamination and subtleties in practical details.…”