[CP2K-user] [CP2K:21390] How to restrain multiple H-bond during metadynamics simulation in CP2K ?

[bijaya pathak]

Dear all, 
I'm trying to do metadynamics simulation in a system, where I need to 
restrain multiple H-bonds. I came across the  constraining colvar 
subsection. 
My input file looks like follows:

&COLVAR 1
       &DISTANCE
          ATOMS 2 60
       &END DISTANCE
 &END COLVAR
&COLVAR 2
       &COORDINATION
          ATOMS_FROM 2
          ATOMS_TO  70 68
          R_0    0.8
          NN 6
          ND 12
       &END COORDINATION
 &END COLVAR
&COLVAR 3
       &COORDINATION
          ATOMS_FROM 61
          ATOMS_TO  8
          R_0    0.8
          NN 6
          ND 12
       &END COORDINATION
 &END COLVAR

&COLVAR 4
       &COORDINATION
          ATOMS_FROM 58
          ATOMS_TO  3
          R_0    0.8
          NN 6
          ND 12
       &END COORDINATION
 &END COLVAR
&COLVAR 5
       &COORDINATION
          ATOMS_FROM 59
          ATOMS_TO  4
          R_0    0.8
          NN 6
          ND 12
       &END COORDINATION
 &END COLVAR

&COLVAR 6
       &COORDINATION
          ATOMS_FROM 1
          ATOMS_TO 66
          R_0    0.8
          NN 6
          ND 12
       &END COORDINATION
 &END COLVAR
&COLVAR 7
     &ANGLE
       ATOMS 2 60 1
     &END ANGLE
&END COLVAR
&CONSTRAINT
    &COLLECTIVE
       COLVAR  2
       TARGET 0.8
       INTERMOLECULAR T
       &RESTRAINT
         K 10
       &END RESTRAINT
    &END COLLECTIVE
    &COLLECTIVE
       COLVAR  3
       TARGET 0.8
       INTERMOLECULAR T
       &RESTRAINT
         K 10
       &END RESTRAINT
    &END COLLECTIVE
    &COLLECTIVE
       COLVAR  4
       TARGET 0.8
       INTERMOLECULAR T
       &RESTRAINT
        K 10
       &END RESTRAINT
    &END COLLECTIVE
    &COLLECTIVE
       COLVAR  5
       TARGET 0.8
       INTERMOLECULAR T
      &RESTRAINT
        K 10
      &END RESTRAINT
    &END COLLECTIVE
     &COLLECTIVE
       COLVAR  6
       TARGET 0.8
       INTERMOLECULAR T
       &RESTRAINT
        K 10
       &END RESTRAINT
    &END COLLECTIVE
    &COLLECTIVE
       COLVAR  7
       TARGET [deg] 170
       INTERMOLECULAR T
       &RESTRAINT
        K 10
       &END RESTRAINT
    &END COLLECTIVE
&END CONSTRAINT
But with small value of force constant, the restrain does not work and when 
I increase the value, the molecules break apart. 
Is there any alternative way to do it ? what am I doing wrong ? Any 
suggestion is appreciated . 
Sincerely 
Bijaya

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