Doubly Tuned Exchange-Correlation Functionals for Mixed-Reference Spin-Flip Time-Dependent Density Functional Theory

It is demonstrated that significant accuracy improvements of MRSF-TDDFT can be achieved by introducing two different XC functionals for the reference Kohn-Sham DFT and the response part of calculations, respectively. Accordingly, two new exchange-correlation (XC) functionals of DTCAM-VEE and DTCAM-AEE were developed on the basis of the "adaptive exact exchange (AEE)" concept in the framework of the Coulomb-attenuating XC functionals. The values by DTCAM-VEE are in excellent agreement with those of Thiel's set (mean absolute error (MAE) and interquartile range (IQR) of 0.218 and 0.327 eV, respectively). On the other hand, DTCAM-AEE faithfully reproduced the qualitative aspects of conical intersections of trans-butadiene and thymine, and the NAMD simulations on thymine. The latter functional also remarkably exhibited the exact 1/R asymptotic behavior of the charge-transfer state of an ethylene-tetrafluoroethylene dimer, and the accurate potential energy surfaces along the two torsional angles of retinal protonated Schiff base model with six double bonds (rPSB6). The current idea can be also applied to other XC functionals as well as other variants of linear response theories, opening a new way of developing XC functionals.