Re: ffTK torsion scan convergence using Gaussian.

From: Gumbart, James C (gumbart_at_physics.gatech.edu)
Date: Tue Nov 13 2018 - 19:56:23 CST

I would guess that it’s a high-energy state, which means you don’t actually need to scan it. FFTK is set to ignore energies above 10 kcal/mol by default anyway. But definitely load the log file and check.

Best,
JC

> On Nov 12, 2018, at 7:08 PM, Dipak Balasaheb Sanap <dipakbs_at_udel.edu> wrote:
>
> Dear all,
> I am trying to parameterize an organic molecule using ffTK. Things run smooth for everything except torsion scan for 1 dihedral. Reading log file suggest that optimization is not converging, I get the following error in log file.
>
> Predicted change in Energy=-1.997999D-02
> Optimization stopped.
> -- Number of steps exceeded, NStep= 120
> -- Flag reset to prevent archiving.
>
> After reading few threads on various mailing lists, I did try few things as follows:
>
> 1. Changed the MaxCycles=1000
> # opt (modredundant,MaxCycles=1000) MP2/6-31g(d) Geom=PrintInputOrient
>
> 2. Tried restart from the existing checkpoint file. Input file for restart as follows:
> %NoSave
> %chk=FRA.scan9.pos.chk
> %nproc=36
> %mem=406GB
> #opt (modredundant,Restart,MaxCyc=1000) MP2/6-31g(d) Guess=Read Geom=Checkpoint
>
> Error for restart:
> Restoring state from the checkpoint file "FRA.scan9.pos.chk".
> ONIOM results not found on unit 2.
>
> I am, attaching the input file any suggestion would be really useful.
> I have also visualized the log file using QM tools, nothing looks broken.
>
> Dipak Sanap
> PhD in Chemistry,
> University of Delaware.
> <FRA.scan9.pos.gau>

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