title: Accurate Theoretical Description of the (1)La and (1)Lb Excited States in Acenes Using the All Order Constricted Variational Density Functional Theory Method and the Local Density Approximation.
abstract: We present the results of calculations on the vertical singlet (1)La and (1)Lb excitation energies in acenes within time dependent density functional theory (TDDFT), second order constricted variational DFT (CV(2)-DFT), and all order constricted variational DFT (CV(∞)-DFT) using the local density approximation LDA(VWN). For the linear acenes it is shown that the application of the Tamm-Dancoff (TD) approximation to TDDFT (TDDFT-TD) substantially improves the agreement with experiment compared to pure TDDFT. This improvement leads to the correct ordering of the (1)La and (1)Lb excitation energies in naphthalene. As TDDFT-TD is equivalent to the second order CV(2)-TD method one might hope for further improvements by going to all orders in CV(∞)-TD. Indeed, for linear acenes the application of the CV(∞)-TD method brings the agreement with experiment to within 0.1 eV for both types of excitations using the simple LDA functional. The CV(∞)-TD method based on LDA is also shown to be accurate for 15 nonlinear acenes with root-mean-square deviations of 0.24 eV for (1)La and 0.17 eV for (1)Lb.
authors.affiliation: Department of Chemistry, University of Calgary , University Drive 2500, Calgary, Alberta, Canada T2N 1N4.
authors.forename: Mykhaylo
authors.initials: M
authors.lastname: Krykunov
authors.affiliation: Mulliken Center for Theoretical Chemistry, Institut für Physikalische und Theoretische Chemie der Universität Bonn , Beringstr. 4, D-53115, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Grimme
authors.affiliation: Department of Chemistry, University of Calgary , University Drive 2500, Calgary, Alberta, Canada T2N 1N4.
authors.forename: Tom
authors.initials: T
authors.lastname: Ziegler