Screened Range-Separated Hybrid Functional with Polarizable Continuum Model Overcomes Challenges in Describing Triplet Excitations in the Condensed Phase Using TDDFT

Abstract

Long range-corrected (LRC) or range-separated hybrid (RSH) functionals where the long-range (LR) limit of electronic interactions is set to the exact exchange have been shown to correct the tendency of traditional density functional theory (DFT) to underestimate the frontier orbital gap. Consequently, the use of such functionals in calculating electronic excited states using linear response based time-dependent DFT (TDDFT) has been successful in correcting the tendency for underestimating the energies of charge transfer states by DFT-based calculations. More recently formulations of functionals that attenuate the LR limit to address condensed-phase effects to polarize the electronic density have been reported. In particular screened RSH (SRSH) combined with polarizable continuum model (PCM) was benchmarked successfully in reproducing the fundamental gap and charge transfer state energies of molecular systems in the condensed phase. Here we use SRSH-PCM to address triplet excited states, and show its success in obtaining correspondence of the low-lying triplet states to the singlet–triplet gap in a similar way that the fundamental orbital gap corresponds to electron removal and addition energies. Importantly, the accuracy of the SRSH-PCM in calculating triplet excitations stands on the polarization consistent framework in addressing the scalar dielectric constant and without affecting the optimal tuning by triplet energies. The prospect of even further improving the SRSH-PCM accuracy in calculating triplet states can be achieved by optimal tuning on the basis of the spin multiplicity gap.

Excited-state properties of organic semiconductor dyes as electrically pumped lasing candidates from new optimally tuned range-separated models

“…Furthermore, we have also relied on a different approach, where the condensed phase is represented by a scalar dielectric constant. 55,71,72 With more details, the solution phase computations were modeled via modifying the constraint α + β = 1 to α + β = 1/ ε , where the asymptotic potential is appropriately screened by the scalar dielectric constant ε . This, in turn, leads to the screened asymptotic behavior correctly in the solvent as 1/ εr instead of 1/ r .…”

“…Furthermore, we have also relied on a different approach, where the condensed phase is represented by a scalar dielectric constant. 55,71,72 With more details, the solution phase computations were modeled via modifying the constraint a + b = 1 to a + b = 1/e, where the asymptotic potential is appropriately screened by the scalar dielectric constant e. This, in turn, leads to the screened asymptotic behavior correctly in the solvent as 1/er instead of 1/r. In this way, the electronic density polarization due to the dielectric environment is addressed by the same preset values of the parameters a and m, while the parameter b is reset from the relation b = (1/e) À a.…”

CTRAMER: An open-source software package for correlating interfacial charge transfer rate constants with donor/acceptor geometries in organic photovoltaic materials

“…In Module 3, TD-DFT is used on selected interfacial D/A molecule pairs to obtain excited states and their partial charges, oscillator strength (OS), and relative energy. 42 These electronic structure protocols are benchmarked against experimental measured excitation energies 28,43,44 (including those of charge transfer states) as well as measured rates. 2,45 We note that, in the condensed phase, as molecules tend to neighbor several molecules, each molecule can be involved in multiple D/A pairs.…”

From Kohn-Sham to many-electron energies via step structures in the exchange-correlation potential

“…In this case each atom within the system can be considered a subsystem. Additional, more complicate examples include donor-acceptor pairs, which are important in photovoltaics [80][81][82][83][84][85] and a molecule between two metallic contacts in a transport experiment [21,28,[86][87][88][89][90]. Therefore, understanding the steps in the exact KS potential is crucial, as it allows one to accurately describe various scenarios in real materials of high practical importance with KS DFT.…”