DFT and TDDFT study of carbon trioxide

Abstract

Carbon trioxide has been studied using DFT and TDDFT methods with different combinations of GGA functionals and correlation consistent basis sets. The C 2 v isomer is calculated to be 2.5 kcal mol −1 and 12.5 kcal mol −1 lower in energy than D 3 h with a conversion energy barrier of 5.0 kcal mol −1 and 12.9 kcal mol −1 by PW91PW91 and B3LYP, respectively. All of the above include zero-point energy corrections. The geometry changes almost linearly along the reaction coordinate and the TS structure is approximately an average of D 3 h and C 2 v with an imaginary O–C–O bending mode of 421 i cm −1. However, D 3 h is more favored in low energy excited singlet states. These states also promote the C 2 v → D 3 h conversion.