[CP2K-user] AIMD under PBC

[Abedi, Mostafa]

Hi Everyone,
I am trying to perform AIMD for a periodic system containing 8 CH4
molecules. Everything goes well, but after a few hundred steps, methane
molecules start to leave the box. This is really strange behavior because
the simulation is running under PBC and if one molecule leaves the box, one
of its images must enter through the opposite face with exactly the same
way and direction. But this is not happening in my simulations. So, it
seems PBC is not working. I believe something is wrong in my input file,
but I can not figure out what it is. I greatly appreciate it if someone
could help me to fix this issue. Many thanks.

&GLOBAL
  PROJECT methane
  RUN_TYPE MD
  WALLTIME 1000000
  PRINT_LEVEL  MEDIUM
&END GLOBAL

&FORCE_EVAL
  METHOD Quickstep
  &DFT
    BASIS_SET_FILE_NAME BASIS_MOLOPT
    POTENTIAL_FILE_NAME GTH_POTENTIALS
    CHARGE 0
    MULTIPLICITY 1
    &MGRID
       CUTOFF [Ry] 400
    &END
    &QS
       METHOD GPW
       EPS_DEFAULT 1.0E-10
       EXTRAPOLATION ASPC
    &END
    &POISSON
       PERIODIC XYZ
       POISSON_SOLVER PERIODIC
    &END
    &SCF
      &PRINT
        &RESTART OFF
        &END
      &END
      SCF_GUESS ATOMIC
      MAX_SCF 30
      EPS_SCF 1.0E-6
      &OT
        PRECONDITIONER FULL_SINGLE_INVERSE
        MINIMIZER CG
      &END OT
      &OUTER_SCF
        MAX_SCF 10
        EPS_SCF 1.0E-6
      &END
    &END SCF
    &XC
      &XC_FUNCTIONAL
       &PBE
       &END
      &END XC_FUNCTIONAL
      &VDW_POTENTIAL
         POTENTIAL_TYPE PAIR_POTENTIAL
         &PAIR_POTENTIAL
            PARAMETER_FILE_NAME dftd3.dat
            TYPE DFTD3
            REFERENCE_FUNCTIONAL PBE
            R_CUTOFF [angstrom] 16
         &END
      &END VDW_POTENTIAL
    &END XC
  &END DFT
   &SUBSYS
    &CELL
      ABC [angstrom] 9.2 9.2 9.2
      PERIODIC XYZ
    &END CELL
    &TOPOLOGY
      COORD_FILE_NAME methane.xyz
      COORD_FILE_FORMAT XYZ
    &END
    &KIND H
      ELEMENT H
      BASIS_SET SZV-MOLOPT-GTH
      POTENTIAL GTH-PBE-q1
    &END KIND
    &KIND C
      ELEMENT C
      BASIS_SET SZV-MOLOPT-GTH
      POTENTIAL GTH-PBE-q4
    &END KIND
  &END SUBSYS
  &PRINT
    &FORCES ON
     FILENAME forces
    &END
  &END
&END FORCE_EVAL

&MOTION
 &GEO_OPT
   OPTIMIZER BFGS
   MAX_ITER  1000
   MAX_DR    [bohr] 0.003
   &BFGS
   &END
 &END
  &MD
   ENSEMBLE NVE
   STEPS 10000
   TIMESTEP 0.5
   TEMPERATURE 500
 &END MD
 &PRINT
   &CELL
    FILENAME cell
   &END
 &END
&END MOTION


Best,
Mostafa
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