How to fix the dihedral angle during the AIMD simulation with CP2K/Quickstep?

[huan... at mail.huji.ac.il]

Dear CP2K users,

I want to fix the dihedral angle of the molecular cluster. The indices of 
the 4 atoms in the cluster are 8, 2, 5, 11, and the corresponding dihedral 
angle is about 26.92 degree.

According to the CP2K manual, I found that the &CONSTRAINT subsection in 
the &MOTION section might be able to deal with it.

Here is my code: 

&MOTION
    &CONSTRAINT
        &COLLECTIVE
             COLVAR 8 2 5 11
             TARGET 26.92      # [degree] 
        &END COLLECTIVE
    &END CONSTRAINT
...
...    


However, CP2K reported an error,
 ************************************************************************
 *** 12:30:45 ERRORL2 in input_parsing:val_create_parsing :: found    ***
 *** unexpected extra argument 2 at , File: 'fix_dihedral_test1.inp',       
  ***
 *** Line: 113, Column: 1, Chunk: <8>                                       
              ***
 ************************************************************************
 
 Looking for words in the input similar to the unknown: 
   '2'

Please see my input file in the attachment. 


This error might result from the setting COLVAR 8 2 5 11 (but this keyword 
does not at Line 113 of the input file... )

I noticed that the keyword COLVAR should specify one index of an atom in 
the molecule, and the subsection of &COLLECTIVE can be repeated. 

Does it correct to write like following?

&MOTION
    &CONSTRAINT
        &COLLECTIVE
             COLVAR 8
        &END COLLECTIVE
        &COLLECTIVE
             COLVAR 2
        &END COLLECTIVE
        &COLLECTIVE
             COLVAR 5
        &END COLLECTIVE
        &COLLECTIVE
             COLVAR 11
        &END COLLECTIVE
...
...

But the TARGET keyword  (value for fixing the dihedral angle to 26.92 
degree) is in the subsection of &COLLECTIVE, NOT in the section of 
&CONSTRAINT.
How can I set the dihedral angle and fix it to 26.92 degree?

I appreciated it if anyone could help me. 

Thanks so much.

Huan
.




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