RAMAN

RAMAN SPECTRUM REQUIRES A PREVIOUSLY COMPUTED $HESS NUCLEAR FORCE CONSTANT MATRIX AS INPUT TO THIS RUN.
PLEASE OBTAIN THIS MATRIX BY A RUNTYP=HESSIAN JOB.
 

$RAMAN group (relevant for all SCFTYPs)

This input controls the computation of Raman intensity by the numerical differentiation produre of Komornicki and others. It is applicable to any wavefunction for which the analytic gradient is available, including some MP2 and CI cases. The calculation involves the computation of 19 nuclear gradients, one without applied electric fields, plus 18 no symmetry runs with electric fields applied in various directions. The numerical second differencing produces intensity values with 2-3 digits of accuracy.
This run must follow an earlier RUNTYP=HESSIAN job, and the $GRAD and $HESS groups from that first job must be given as input. If the $DIPDR is computed analytically by this Hessian job, it too may be read in, if not, the numerical Raman job will evaluate $DIPDR. Once the data from the 19 applied fields is available, the $ALPDR tensor is evaluated. Then the nuclear derivatives of the dipole moment and alpha polarizability will be combined with the normal coordinate information to produce the IR and Raman intensity of each mode.
To study isotopic substitution speedily, input the $GRAD, $HESS, $DIPDR, and $ALPDR groups along with the desired atomic masses in $MASS.
The code does not permit any semi-empirical or solvation models to be used.
EFIELD = applied electric field strenth. The literature suggests values in the range 0.001 to 0.005. (default = 0.002 a.u.)
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$ALPDR group (relevant for RUNTYP=RUNTYP=RAMAN or HESSIAN)
Formatted alpha derivative tensor, punched by a previous RUNTYP=RAMAN job. If both
$DIPDR and this group are found in the input file, the applied field computation will be
skipped, to immediately evaluate IR and Raman intensities.
If this group is found during a Hessian job, the Raman intensities will be added to the
output. You might want to run as RUNTYP=HESSIAN instead of RUNTYP=RAMAN in order
to have access to PROJCT or the other options available in the $FORCE group.