Tuned Range-Separated Time-Dependent Density Functional Theory Applied to Optical Rotation

For range-separated hybrid density functionals, the consequences of using system-specific range-separation parameters (gamma) in calculations of optical rotations (ORs) are investigated. Computed ORs at three wavelengths are reported for methyloxirane, norbornenone, beta-pinene, [6]helicene, [7]helicene, and two derivatives of [6]helicene. The gamma parameters are adjusted such that Kohn-Sham density functional calculations satisfy the condition -epsilon(HOMO) (N) = IP. For beta-pinene, the behavior of the energy as a function of fractional total charge is also tested. For the test set of molecules, comparisons of ORs with available coupled-cluster and experimental data indicate that the gamma tuning leads to improved results for beta-pinene and the helicenes and does not do too much harm in other cases.