Resonance Raman

According to a the time-dependent picture of resonance-Raman scattering the relative intensities of RR scattering cross sections are, under certain assumptions, proportional to the square of the excited-state energy gradients projected onto the ground-state normal modes of the molecule (see Ref. [202]).

Such excited-state gradients can be computed numerically by ADF's VIBRON module, which is invoked by selecting the VIBRON runtype in the GEOMETRY block key, the use of the VIBRON block key and the EXCITATION block key:

GEOMETRY
  VIBRON
END

VIBRON
 NMTAPE filename
 RESRAMAN
 {...
 ..}
END

EXCITATIONS
  LOWEST nlowest
END

The VIBRON module always requires an EXCITATIONS input block, in which the total number of excited states to be calculated must be specified. NMTAPE is the only obligatory keyword for the VIBRON module. It specifies the name of a TAPE21 file from a previous frequency calculation. This TAPE21 file is needed to read the normal modes w.r.t. which the derivatives are computed. I.e., a separate frequency calculation must be carried out first. The second subkeyword RESRAMAN invokes the resonance Raman calculation. Note that the VIBRON module is not suited for open-shell TDDFT.