A vibrational circular dichroism implementation within a Slater-type-orbital based density functional framework and its application to hexa- and hepta-helicenes

Wedescribe the implementation of the rotational strengths for vibrational circular dichroism (VCD) in theSlater-typeorbital basedAmsterdamDensity Functional (ADF)package.We show that our implementation, which makes use of analytical derivative techniques and London atomic orbitals, yields origin independent rotational strengths. The basis set dependence in the particular case of Slater-type basis functions is also discussed. It turns out that the triple zeta STO basis sets with one set of polarization functions (TZP) are adequate for VCD calculations. The origindependence of the atomic axial tensors is checked by a distributed origin gauge implementation. The distributed and common origin gauge implementations yield virtually identical atomic axial tensors with the Slatertype basis sets employed here, proving that our implementation yields origin independent rotational Electronic supplementary material The online version of this article (doi:10.1007/s00214-006-0234-x) contains supplementary material, which is available to authorized users. V. P. Nicu (B) · E. J. Baerends (B) Theoretical Chemistry, Vrije Universiteit Amsterdam, De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands e-mail: [email protected] E. J. Baerends e-mail: [email protected] J. Neugebauer Laboratorium für Physikalische Chemie, ETH Zurich, Wolfgang-Pauli-Strasse 10, 8093 Zurich, Switzerland e-mail: [email protected] S. K. Wolff Nanochemistry Research Institute, Department of Applied Chemistry, Curtin University of Technology, P.O. Box U 1987, Perth, WA 6845, Australia e-mail: [email protected] strengths. We verify the implementation for a set of benchmark molecules, for which the dependence of the VCD spectra on the particular choice of the exchange– correlation functional is studied. The pure functionals BP86 and OLYP show a particularly good performance. Then, we apply this approach to study the VCD spectra of hexaand heptahelicenes. In particular we focus on relationships between the signof the rotational strengths of the two helicenes.