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Alexei Popov
alexei.a.popov@gmail.com

this can be the case when the step along torsion is large
and crosses singular values of +180 and -180 degrees.
In your particular case, the initial step (100 deg.)
is really huge, while all other are not. You need to
open your molecule in any model builder program -
e.g. you can use ChemCraft - and change the torsion as
appropriate rotating along the proper pair of atoms,
then use the updated geometry for scan.

-Alexei



On Wed Sep 29 '10 6:56pm, Slava wrote
-------------------------------------
>Here are my inputs:

> 1 - works fine

> $contrl scftyp=rhf nzvar=93 runtyp=rsurface dfttyp=b3lyp1 exetyp=run $end
> $contrl maxit=300 icharg=0 coord=cart $end
> $system mwords=260 timlim=9999 mklnp=2 $end
> $basis gbasis=N31 ngauss=6 diffsp=.t. ndfunc=1 $end
> $scf dirscf=.t. $end
> $statpt opttol=5d-4 nstep=50 method=gdiis noreg=5 itbmat=50 $end
> $surf disp1=20 orig1=0 ndisp1=18 reuse=.t. $end
> $p2p p2p=.t. dlb=.t. $end
> $zmat ifdmod=2 dlc=.t. auto=.t. autofv=.t. ifzmat(1)=3,3,1,13,16
> scan=.t. irzmat(1)=3,3,1,13,15, 3,3,1,13,14 $end
> $data
> c4mimotf Bu-top torsion, scan 6-31G+(d)
>C1
>...
> $END

>2 - execution crashes

> $contrl scftyp=rhf nzvar=93 runtyp=rsurface dfttyp=b3lyp1 exetyp=run $end
> $contrl maxit=300 icharg=0 coord=cart $end
> $system mwords=260 timlim=9999 mklnp=2 $end
> $basis gbasis=N31 ngauss=6 diffsp=.t. ndfunc=1 $end
> $scf dirscf=.t. $end
> $statpt opttol=5d-4 nstep=50 method=gdiis noreg=5 itbmat=50 $end
> $surf disp1=5 orig1=-100 ndisp1=5 reuse=.t. $end
> $p2p p2p=.t. dlb=.t. $end
> $zmat ifdmod=2 dlc=.t. auto=.t. autofv=.t. ifzmat(1)=3,3,1,13,16
> scan=.t. irzmat(1)=3,3,1,13,15, 3,3,1,13,14 $end
> $data
> c4mimotf Bu-top torsion, scan 6-31G+(d) in the vicinity of second minimum
>C1
>... the same as in 1...
> $END

>On Wed Sep 29 '10 10:13am, Slava wrote
>--------------------------------------
>>Dear folks!
>>I have a following problem. I use FF to perform RSC of a selected dihedral. When I scaned dihedral in a range of (0 - 360) deg, everything was ok, execution begun and ended normally. But when I wanted to perform more precise scan in the vicinity of minimum and changed range of scanning(and step), I got an error, something like this 'transforming displacements from internals to cartesians can not be performed'. Moreover, RMS error in iteration increase with the increase of number of iterations, that makes no sense in increasing itbmat. I tried to find sollution in a related posts, but I didn't succeed in it. What is going wrong? The first and the second input are practically the SAME!

>>Regards,
>>Sviataslau Kohut