Molcas Forum

jiang663

Member

Registered: 2022-03-01

Posts: 5

How to scan reaction coordinates

Hi,

I just have a question on internal reaction coordinate using.

(1) Currently I am running azobenzene and want to calculate different CNNC dihedral angle. Is it available for Openmolcas to make the scan on internal coordinates? (for example, scan CNNC dihedral angle 10 times, each step is 2 degree) (I searched manual and only find the fixed internal reaction coordinate but didn't find how to scan).

(2) Also, if it is okay for scan, is it okay to output the Cartesian coordinate of each scan? (even without any wavefunction calculation, since I only need the Cartesian coordinates in each grid on internal coordinates)

Ignacio

Administrator

From: Uppsala

Registered: 2015-11-03

Posts: 1,085

Re: How to scan reaction coordinates

If you mean a "rigid" scan, i.e. change only the dihedral and keep all other internal coordinates frozen, that's not possible.

If you mean a "relaxed" scan, where you fix the dihedral to different values and optimize all the other coordinates to minimize the energy, you can do that with a constraint and a FOREACH loop, e.g.

> FOREACH D in (60,62,64,66)
&GATEWAY
  ...
  Constraints
    d = Dihedral C1 N2 N3 C4
   Values
    d = $D
  End of Constraints

  > DO WHILE
    &SEWARD
    &SCF
    &SLAPAF
  > END DO
> END FOREACH

In this case your (2) does not make sense, because in order to obtain the coordinates you have to do the wfn calculations first.