mentioned in the title problem arose several times when I tried to calculate TDDFT spectra of molecules with high internal symmetry (benzene, ferrocene, etc.). Usually, almost all transitions in the calculated TDDFT spectrum were of zero oscillator strength (you can find an example attached to this message).
Actually, this problem did not make me worried until I had to calculate a series of bis-cyanine dyes with their molecules of C2 of Ci symmetry. Their spectra did not contain any "zero-f" transitions, but the oscillator strengths of the long-wavelength transitions were really strange (in some cases the maximum values of f were obtained for symmetry-forbidden transitions).
PS NOSYM=1 in the $CONTRL group does not solve the problem, as well ISTSYM=0 in the $TDDFT group
Will be thankful for any advice.
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[ ferr_ci_td.zip ] ferrocene TDDFT task