FIG. 8.
(a) Absorption spectra of the Mg-chlorin chromophore of Chl a (structure shown), comparing a gas-phase experimental spectrum202 to a ΔSCF calculation at the B97M-V/def2-TZVPD level, which is then spin-purified using Eq. (7).200 (b) Four-orbital model demonstrating the states that were targeted using the STEP algorithm and included in the excitation spectrum shown in (a). Adapted with permission from K. Carter-Fenk and J. M. Herbert, J. Chem. Theory Comput. 16, 5067 (2020). Copyright 2020 American Chemical Society.