title: Extensions of the Time-Dependent Density Functional Based Tight-Binding Approach.
abstract: The time-dependent density functional based tight-binding (TD-DFTB) approach is generalized to account for fractional occupations. In addition, an on-site correction leads to marked qualitative and quantitative improvements over the original method. Especially, the known failure of TD-DFTB for the description of σ → π* and n → π* excitations is overcome. Benchmark calculations on a large set of organic molecules also indicate a better description of triplet states. The accuracy of the revised TD-DFTB method is found to be similar to first principles TD-DFT calculations at a highly reduced computational cost. As a side issue, we also discuss the generalization of the TD-DFTB method to spin-polarized systems. In contrast to an earlier study, we obtain a formalism that is fully consistent with the use of local exchange-correlation functionals in the ground state DFTB method.
authors.affiliation: Bremen Center for Computational Materials Science, Universität Bremen , Am Fallturm 1, 28359 Bremen, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Domínguez
authors.affiliation: Bremen Center for Computational Materials Science, Universität Bremen , Am Fallturm 1, 28359 Bremen, Germany.
authors.forename: B
authors.initials: B
authors.lastname: Aradi
authors.affiliation: Bremen Center for Computational Materials Science, Universität Bremen , Am Fallturm 1, 28359 Bremen, Germany.
authors.forename: T
authors.initials: T
authors.lastname: Frauenheim
authors.affiliation: Department of Theoretical Physics, University of Regensburg , 93040 Regensburg, Germany.
authors.forename: V
authors.initials: V
authors.lastname: Lutsker
authors.affiliation: Department of Theoretical Physics, University of Regensburg , 93040 Regensburg, Germany.
authors.forename: T A
authors.initials: TA
authors.lastname: Niehaus