## Firefly and PC GAMESS-related discussion club

Learn how to ask questions correctly

** Re: Relaxed scan along bending mode across linear structure **
Pedro Silva

pedros@ufp.edu.pt

On Fri Jan 19 '18 3:44pm, Bernhard Dick wrote

---------------------------------------------

>I want to follow a bending mode from 120° to 240°, i.e. the linear structure at 180° is in the middle and presumably a transition state. I try using RSURFACE with DLC, e.g.:> $SURF NDISP1=25 DISP1=5.0 ORIG1=120.0 REUSE=.F. NSURF=1 $END

> $zmat ifdmod=1 dlc=.t. auto=.t. autofv=.t. ifzmat(1)=2,3,2,4 scan=.t.

> DLCTOL=1D-7 ORTTOL=1D-7 CNVTOL=1D-7 NONVDW(1)=1,2 $end

>The connectivity of the atoms is 3-2-4-1, and the angle 2-4-1 is always ca. 100°. The calculation stops when the angle 3-2-4 gets close to 180° due to convergence problems with the DLCs. I reduced some of the tolerances and played with IFDMOD=0,1,2 and REUSE=T/F, but there are many combinations, and I did not find one that works.

>I wonder whether anybody did this before and knows a trick?

>best regards, Bernhard

>

On Fri Jan 19 '18 3:44pm, Bernhard Dick wrote

---------------------------------------------

>I want to follow a bending mode from 120° to 240°, i.e. the linear structure at 180° is in the middle and presumably a transition state. I try using RSURFACE with DLC, e.g.:

> $SURF NDISP1=25 DISP1=5.0 ORIG1=120.0 REUSE=.F. NSURF=1 $END

> $zmat ifdmod=1 dlc=.t. auto=.t. autofv=.t. ifzmat(1)=2,3,2,4 scan=.t.

> DLCTOL=1D-7 ORTTOL=1D-7 CNVTOL=1D-7 NONVDW(1)=1,2 $end

>The connectivity of the atoms is 3-2-4-1, and the angle 2-4-1 is always ca. 100°. The calculation stops when the angle 3-2-4 gets close to 180° due to convergence problems with the DLCs. I reduced some of the tolerances and played with IFDMOD=0,1,2 and REUSE=T/F, but there are many combinations, and I did not find one that works.

>I wonder whether anybody did this before and knows a trick?

>best regards, Bernhard

>

I have met some success in these situation by including a nonvdw(1) instruction between one of the ends of the linear structure and an "off"-linear atom. In your case, I would include:

$zmat nonvdw(1)=3,1

Mon Jan 22 '18 7:34pm

This message read **27** times