We present a new approach to calculating potential energy surfaces for photochemical reactions by combining self-consistent-field calculations for single-reference ground and excited states with symmetry-corrected spin-flip Tamm-Dancoff approximation calculations for multireference electronic states. The method is illustrated by an application with the M05-2X exchange-correlation functional to cis-trans isomerization of the penta-2,4-dieniminium cation, which is a model (with three conjugated double bonds) of the protonated Schiff base of retinal. We find good agreement with multireference configuration interaction-plus-quadruples (MRCISD+Q) wave function calculations along three key paths in the strong-interaction region of the ground and first excited singlet states.
Xu, Xuefei; Gozem, Samer; Olivucci, Massimo; and Truhlar, Donald G., "Combined Self-consistent-field And Spin-flip Tamm-dancoff Density Functional Approach To Potential Energy Surfaces For Photochemistry" (2013). Chemistry Faculty Publications. 174.
Journal Of Physical Chemistry Letters