Combined Self-Consistent-Field and Spin-Flip Tamm–Dancoff Density Functional Approach to Potential Energy Surfaces for Photochemistry

• Published in: The journal of physical chemistry letters Vol. 4; no. 2; pp. 253 - 258
• Main Authors: Xu, Xuefei, Gozem, Samer, Olivucci, Massimo, Truhlar, Donald G
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 17.01.2013
• Subjects: Spectroscopy, Photochemistry, and Excited States; time-dependent density functional theory; SF2 method; multireference configuration interaction; broken symmetry; electronically excited states; conical intersection
• ISSN: 1948-7185; 1948-7185
• DOI: 10.1021/jz301935x

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.