Do I have an imaginary frequency?


Clicked A Few Times
Hi all

I have performed a frequency calculation on a non-linear molecule, and these are the first 12 projected frequencies:

P.Frequency
-32.99
0.00
0.00
0.00
0.00
0.00
0.00
56.85
77.48
116.62
154.38
250.92

Am I at a local minimum, or am I at a local maximum with one imaginary vibrational mode? I suspect the latter, but when I open the file in Avogadro, it does not list the -32.99 cm^-1 vibration.

Forum Vet
Yes, it looks like you have an imaginary frequency and are not in the global minimum. You may want to contact Marcus Hanwell, the lead Avogadro developer, as I believe this may be an error on their part in handing the output file.

Thanks,

Bert


Quote:Andrew.yeung Nov 9th 4:01 am
Hi all

I have performed a frequency calculation on a non-linear molecule, and these are the first 12 projected frequencies:

P.Frequency
-32.99
0.00
0.00
0.00
0.00
0.00
0.00
56.85
77.48
116.62
154.38
250.92

Am I at a local minimum, or am I at a local maximum with one imaginary vibrational mode? I suspect the latter, but when I open the file in Avogadro, it does not list the -32.99 cm^-1 vibration.

Clicked A Few Times
Any tips on how to get rid of these tiny imaginary frequencies? This structure was optimized at the b3lyp/cc-pvtz (spherical) level. The input geometry was had been optimized to a local minimum (no imaginary frequencies) at the same level in Gaussian 09.

I've tried the suggestions in http://nwchemgit.github.io/Special_AWCforum/st/id383/#post_1289 with no luck.

Forum Vet
Andrew,
Could you send us the geometry of the molecule?

Thanks, Edo


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