$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 inputs 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, provide $GRAD,
$HESS, $DIPDR, and $ALPDR inputs, along with the desired
atomic masses in $MASS.
The code does not permit semi-empirical or solvation
models to be used.
EFIELD = applied electric field strength. The literature
suggests values in the range 0.001 to 0.005.
(default = 0.002 a.u.)
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generated on 7/7/2017
