Setting individual restraints for various atoms

Florian Gisdon florian... at googlemail.com
Thu Apr 7 11:48:13 CEST 2016


Dear cp2k community,

I am new to cp2k and try to set up a QMMM system with the MM part gradually 
restraint, starting totally flexible close to the QM region and getting 
more and more stiff further away. So far I've just found the 
CP2K_INPUT / MOTION / CONSTRAINT / COLLECTIVE / RESTRAINT subsection, where 
I can specify some harmonic force constant for some collective variable. 
To restrain an atom I thought about the CP2K_INPUT /FORCE_EVAL / SUBSYS / 
COLVAR / XYZ_DIAG subsection to specify the atom and its component. With 
that it should be possible to assign individual restraints.
I thought about a setup like that:

Definition of the colvar

&FORCE_EVAL
  &SUBSYS
    &COLVAR
      &XYZ_DIAG
        ATOM 1
        COMPONENT X
      &END XYZ_DIAG
    &END COLVAR
  &END SUBSYS
&END FORCE_EVAL

and definition of the restraint

&MOTION
  &CONSTRAINT
     &COLLECTIVE
        COLVAR 1
        INTERMOLECULAR .TRUE.
        &RESTRAINT
           K 0.015
        &END RESTRAINT
     &END COLLECTIVE
  &END CONSTRAINT
&END MOTION

Is this the right way to go? If so, then it should be defined for each 
component of several hundred atoms. Is there an easier way to achieve this?

Many thanks


Florian
<https://manual.cp2k.org/cp2k-3_0-branch/CP2K_INPUT/MOTION/CONSTRAINT/COLLECTIVE.html>
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