Do I have an imaginary frequency?
Clicked A Few Times
9:01:25 PM PST - Thu, Nov 8th 2012
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
10:50:15 AM PST - Fri, Nov 9th 2012
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
11:11:00 AM PST - Tue, Nov 13th 2012
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
1:22:24 PM PST - Tue, Nov 13th 2012
Andrew,
Could you send us the geometry of the molecule?

Thanks, Edo


Forum >> NWChem's corner >> Running NWChem