[CP2K-user] Problems to contraint the z axis of an atom

[qin li]

Dear CP2K users and developers,  
        I'm using cp2k7.1 to restrain an atom in a target position in z 
axis, but the distance subsection does not work fine as i expected. The 
target z axis of the atom (9.2) is in a metastable state in MD without 
constraint and close to to its initial z coordination (9.18), but when i 
add the constraint on it, the output of the z coordination turn out to be 
around 9.4,  which is not 9.2, so i'm puzzled if there is some issues in my 
input. Here are my input to define the CV and constraint:
     &COLVAR
       &DISTANCE
         &POINT
           TYPE FIX_POINT
           XYZ 0.0 0.0 9.20
         &END POINT
         &POINT
           ATOMS 39
         &END POINT
         AXIS Z
         POINTS 2 1
       &END DISTANCE
     &END COLVAR

   &CONSTRAINT
     &CONSTRAINT_INFO
       &EACH
         MD 1
       &END
     &END
     &COLLECTIVE
       COLVAR 1
       INTERMOLECULAR
       TARGET 0.0
       &RESTRAINT
         K  10.0
       &END
     &END
   &END

Thanks in advance,  
Qin Li 

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