Vibronic coupling and double excitations in linear response time-dependent density functional calculations: dipole-allowed states of N2

The vibronic coupling effect and double excitations were studied using time-dependent density functional response theory (TDDFRT). The density function calculations were performed using a modified version of the Amsterdam density functional (ADF) package. A combination of statistical averaging of orbital potentials (SAOP) and TDDFRT calculations was found to be efficient in the qualitative simulation of vibronic structure of larger molecules. The vibronic coupling calculations showed that the shapes of adiabatic potential energy curves of the TDDFRT/SAOP calculations were satisfactory.