In this method (Ref.[266]) the resonance Raman-scattering (RRS) spectra is calculated from the geometrical derivatives of the frequency-dependent polarizability. The polarizability derivatives are calculated from resonance polarizabilities by including a finite lifetime (phenomenological parameter) of the electronic excited states using time-dependent density-functional theory.
It is similar to the simple excited-state gradient approximation method (see next section) if only one electronic excited state is important, however, it is not restricted to only one electronic excited state. In the limit that there is only one possible state in resonance the two methods should give more or less the same results. However, for many states and high-energy states and to get resonance Raman profiles (i.e., Raman intensities as a function of the energy of the incident light beam) this approach might be more suitable. The resonance Raman profiles in this approach are averaged profiles since vibronic coupling effects are not accounted for. At the moment this method needs numerically calculated frequencies in Cartesian coordinates. The method described in the next section can use a basis of normal coordinates rather than Cartesian coordinates, so that in that method the calculation can be restricted to a couple of modes.
GEOMETRY
FREQUENCIES
END
ALLPOINTS
AORESPONSE
RAMAN
FREQUENCY 1 freq1 units
LIFETIME width
END
This method needs ALLPOINTS, because of the AORESPONSE key, and numerically calculated frequencies. The RRS is not calculated if one uses symmetric displacements in the numerically calculated frequencies or if one uses analytically calculated frequencies. The documentation of the AORESPONSE key explains in more detail the meaning of the subkeywords in the block key AORESPONSE, which are required to calculate RRS. Similarly to the normal Raman module, the AOREPONSE-Raman only works with one frequency.
