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 (γ) in calculations of optical rotations (ORs) are investigated. Computed ORs at three wavelengths are reported for methyloxirane, norbornenone, β-pinene, [6]helicene, [7]helicene, and two derivatives of [6]helicene. The γ parameters are adjusted such that Kohn-Sham density functional calculations satisfy the condition -ε ^HOMO(N) = IP. For β-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 γ "tuning" leads to improved results for β-pinene and the helicenes and does not do too much harm in other cases.