MOPAC opt + freq

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Posts: 21
Joined: Sat Jun 20, 2020 3:37 am
Full Name: John Keller
Organization: University of Alaska Fairbanks
Subdiscipline: Chemistry

MOPAC opt + freq

Post by jwk »

Please consider adding an "opt + freq" option for MOPAC.
Under Calculation in the Job Options tab for MOPAC, WebMO offers only separate choices of Geometry Optimization and Vibrational Frequencies. However, Gaussian and other QM packages offer Optimize + Vib Freq options, which is very useful. It turns out that MOPAC also can do this type of combination job, and it is correctly parsed by WebMO, i.e. both the Geometry Sequence and Vibrational Modes tables appear on the View Job page. This requires an additional line "oldgeo force" following a blank line after the main input section. For example, see WebMO demo job # 701421.
Because of the all-too-frequent occurence of symmetric transition-state geometries, routine freq calculations are recommended for almost all geometry optimizations, so why not combine them?

Posts: 40
Joined: Sat May 30, 2020 3:00 pm
Full Name: JR Schmidt
Organization: WebMO, LLC

Re: MOPAC opt + freq

Post by schmidt »

This is interesting! I was not aware that jobs could be "chained" in MOPAC like this. Be aware that, according to the docs, one would need to repeat other keywords (such as PM7) in both calculations.

I will look to see if we can add this job to the next minor release.

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