A dressed TDDFT treatment of the 2Ag states of butadiene and hexatriene

The nature and energetics of the low-lying singlet states of polyenes have presented significant challenges for electronic structure methods. This is particularly true for conventional implementations of time-dependent density functional theory (TDDFT), which, because of their use of the adiabatic approximation, have difficulty in describing states of ‘doubly-excited character’. We show that use of our recently developed ‘Dressed TDDFT’ approach provides a compact and accurate method for treating these doubly excited states, by use of a frequency-dependent exchange-correlation kernel. We present results for the vertical absorption energy for the 2Ag states of butadiene and hexatriene, and the vertical fluorescence and 0–0 transitions for the 2 Ag state of butadiene. 2004 Elsevier B.V. All rights reserved.