Combined gradient projection/single component artificial force induced reaction (GP/SC-AFIR) method for an efficient search of minimum energy conical intersection (MECI) geometries

Abstract

We report a new approach to search for structures of minimum energy conical intersection (MECIs) automatically. Gradient projection (GP) method and single component artificial force induced reaction (SC-AFIR) method were combined in the present approach. As case studies, MECIs of benzene and naphthalene between their ground and first excited singlet electronic states (S 0 /S 1-MECIs) were explored. All S 0 /S 1-MECIs reported previously were obtained automatically. Furthermore, the number of force calculations was reduced compared to the one required in the previous search. Improved convergence in a step in which various geometrical displacements are induced by SC-AFIR would contribute to the cost reduction.

Locating conical intersections using the quasidegenerate partially and strongly contracted NEVPT2 methods

“…Here, the ⟨S 2 ⟩ values at the two states are summarized in Table 3. These values are similar to those at the SF-TD-DFT/6-31G(d) level of theory obtained by Harabuchi [44]. The highest ⟨S 2 ⟩ value found in this study was greater than one (for S 1 at the global minimum structure).…”

“…The numbering is consistent with that in Ref. [44]. The computed excitation energies for the global minimum (D 6h ) structure were 4.98, 5.35, 4.87, and 5.33 eV according to the CASSCF, PC-NEVPT2, CASPT2, and SF-TD-DFT levels of theory, respectively.…”

“…In the SF-TD-DFT [41] calculation, restricted open-shell triplet wavefunctions were employed as a reference, and the BHHLYP functional [42,43] was employed as in Ref. [44]. An imaginary level shift [22] of 0.2i and density fitting were applied in the XMS-CASPT2 calculations.…”

“…As a pilot application of QD-NEVPT2, CIs located by Harabuchi et al at the SF-TD-DFT/6-31G(d) level of theory [44] were relocated using the CASSCF, PC-NEVPT2, SC-NEVPT2, CASPT2, and SF-TD-DFT methods using the cc-pVTZ basis set. In Table 1, the energies of eight MECIs relative to the lowest MECI 1 at SF-TD-DFT are summarized, and the optimized structures with PC-NEVPT2 are shown in Figure 1.…”

Excited‐State Reactivity of [Mn(im)(CO)3(phen)]+: A Structural Exploration

“…To obtain an overview of the primary events taking place on the S 2 PES that corresponds to the absorbing state, MECI structures and paths passing them were explored using the AFIR method . MECIs between the first‐ and second‐excited singlet states ( S 1 / S 2 ‐MECIs) were searched by the single‐component AFIR (SC‐AFIR) algorithm combined with the GP type optimizer . In the search, the structural deformation around the Mn center is explored by setting the target atoms in the SC‐AFIR algorithm to seven atoms, that is, Mn, three carbon atoms in carbonyl, and three nitrogen atoms connected to the Mn atom.…”