CCL:G: convergence-maximum displacement
- From: Orlin Blajiev <blajiev . vub.ac.be>
- Subject: CCL:G: convergence-maximum displacement
- Date: Wed, 5 Nov 2008 00:18:46 +0100 (CET)
Sent to CCL by: Orlin Blajiev [blajiev^^vub.ac.be]
I would like to post again the question about how to neglect the "Maximum
Displacement 0.125614 0.007200 NO" convergence option in
Gaussian. I would like just to proceed to a frequency calculation.
Thanks very much in advance.
>Sent to CCL by: "Kalju Kahn" [kalju+/-chem.ucsb.edu]
>If you loosen these criteria too much, you will have a successful
>calculation but the structure found will be too far from the true minimum.
> Being able to do a calculation is not the same thing as being able to get
>the correct result.
>If you really want to neglect displacement conditions, just use the
>geometry that gave the results below (or pick a geometry with the lowest
>energy from your search).
>Your forces are small, the PES must be very flat in the region you are in:
>large changes in the structure will cause only small change in energy.
>You may want to make sure that your structure is a minimum, not a saddle
>point or a some plateau via frequency calculation. You should not have
>negative frequencies. After the frequency calculation, it will not hurt
>to try Opt=ReadFC, Geom=Check; you might find a better structure quickly
>using the correct Hessian.
>> Sent to CCL by: Orlin Blajiev [blajiev%x%vub.ac.be]
>> I will appreciate an advise how to relax Maximum Displacement
>> (or neglect it althogether). I am already using IOP(1/7=1200).
>> Maximum Force 0.000275 0.001800 YES
>> RMS Force 0.000063 0.001200 YES
>> Maximum Displacement 0.125614 0.007200 NO
>> RMS Displacement 0.017703 0.004800 NO
>> Thank in advance.
>> Orlin Blajiev
>> Electrochemical and Surface Engineering (SURF)
>> Faculty of Applied Science
>> Vrije Universiteit Brussel
>> Pleinlaan 2 - 1050 Brussels - Belgium
>> tel: ++32 2 6293538 - fax: ++32 2 6293200>
>Dr. Kalju Kahn
>Department of Chemistry and Biochemistry
>UC Santa Barbara, CA 93106>
Electrochemical and Surface Engineering (SURF)
Faculty of Applied Science
Vrije Universiteit Brussel
Pleinlaan 2 - 1050 Brussels - Belgium
tel: ++32 2 6293538 - fax: ++32 2 6293200