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Alex Granovsky
gran@classic.chem.msu.su

just a couple of comments in the hope they are of some help.

1. I have carefully examined the source code and I have to confirm
there exists a bug in the printout section of the vibrational
analysis code. Namely, under some exotic circumstances, the "I"
marker used to designate imaginary frequencies, is not properly
printed out. Moreover, under the same circumstances, the translation
and rotation modes will not be properly picked up. This problem
will be fixed in the forthcoming releases. As far as I understand,
in the printout you attached, all frequencies in the initial region
up to 143.21 cm^-1 are imaginary, then goes 6 T+R modes,
and the rest are the real vibrations.

2. Note, one does not need to set ISTATE for state-specific MCSCF
gradient runs. Moreover, by setting ISTATE one selects the alternative,
more general but somewhat less accurate and computationally more
expensive approach to calculate gradients. The molecular system
you are studying is extremely non-rigid, so one needs to optimize
it tightly using opttol equal to at least 10^-4 or below,
then use  $force nvib=2 $end for Hessian.

Regards,
Alex Granovsky




On Tue Feb 8 '11 10:58pm, Jonas Baltrusaitis wrote
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>Dear all,

>tried MCSCF optimization+freq in ground state, calculated frequencies but got huge amount of reversed magnitude frequencies, e.g. no negatives but after frequencies come close to zero they suddenly start increasing again. I bet it's because of MCSCF but not sure what it means or how to respond to it

>see attached

>Jonas