[molpro-user] unexpected imaginary frequency

Venkatesan S. Thimmakondu venkateshtsv at gmail.com
Sun Mar 25 05:00:17 BST 2012

The potential along the CNH2 out-of-plane motion, which caused the
imaginary frequency, seems to be "pretty flat" at this level of theory.
This could be one of the reasons why you got an imaginary frequency.
Enclosed, please find the plot.

In cases like this, it is better to use a basis set, which has more diffuse

On Fri, Mar 23, 2012 at 8:08 PM, Charles E Cotton <ccotton at purdue.edu>wrote:

> I used the experimental geometry for formamide to do a CCSD(T)/AVDZ geom
> opt and subsequent frequency calculation.
> The optimization converges after a few cycles, but the resulting freq
> calculation results with one imaginary frequency.
> This structure should be a minimum, and ideas why I'd get an imaginary at
> approx 30CM-1?
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