MOPAC Dihedral Search

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KJohnson@PacificU
Posts: 1
Joined: Wed Sep 08, 2021 7:13 pm
Full Name: Kevin Johnson
Organization: Pacific University
Subdiscipline: Physical Chemistry

MOPAC Dihedral Search

Post by KJohnson@PacificU »

It appears that when I set up a dihedral angle search MOPAC interprets a '0.00' in the list of search angles to be a bond distance. Is the job input correctly formatted for a dihedral search?
Appending the Job Output for HOOH dihedral search:


POINTS ON REACTION COORDINATE
-1.00 0.00 5.00 10.00 15.00 20.00 25.00 30.00
35.00 40.00 45.00 50.00 55.00 60.00 65.00 70.00
75.00 80.00 85.00 90.00 95.00 100.00 105.00 110.00
115.00 120.00 125.00 130.00 135.00 140.00 145.00 150.00
155.00 160.00 165.00 170.00 175.00 180.00 185.00 190.00
195.00 200.00 205.00 210.00 215.00 220.00 225.00 230.00
235.00 240.00 245.00 250.00 255.00 260.00 265.00 270.00
275.00 280.00 285.00 290.00 295.00 300.00 305.00 310.00
315.00 320.00 325.00 330.00 335.00 340.00 345.00 350.00
355.00 360.00

INTERATOMIC SEPARATION IS ZERO FOR POINT 2 ON REACTION PATH

******************************************************************************
* *
* Error and normal termination messages reported in this calculation *
* *
* INTERATOMIC SEPARATION IS ZERO FOR POINT 2 ON REACTION PATH *
* JOB ENDED NORMALLY *
* *
******************************************************************************

schmidt
Posts: 42
Joined: Sat May 30, 2020 3:00 pm
Full Name: JR Schmidt
Organization: WebMO, LLC

Re: MOPAC Dihedral Search

Post by schmidt »

This is a MOPAC bug which I have encountered before. For some reason, MOPAC does not like the number "0" (exactly) in a dihedral scan, although there is no reason why it should (in principle) be problematic. Simply avoiding zero (e.g. 1 degree) yields the expected result.

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