&FORCE_EVAL
  METHOD FIST
  &MM
    &FORCEFIELD
      parm_file_name ../sample_pot/water.pot
      parmtype CHM
      &CHARGE
        ATOM OT
        CHARGE -0.8476
      &END CHARGE
      &CHARGE
        ATOM HT
        CHARGE 0.4238
      &END CHARGE
    &END FORCEFIELD
    &POISSON
      &EWALD
        EWALD_TYPE pme
        ALPHA .44
        NS_MAX 25
      &END EWALD
    &END POISSON
  &END MM
  &SUBSYS
    &CELL
      ABC 24.955 24.955 24.955
    &END CELL
    &TOPOLOGY
      COORD_FILE_NAME ../sample_pdb/water_2.pdb
      COORDINATE pdb
    &END TOPOLOGY
  &END SUBSYS
&END FORCE_EVAL
&GLOBAL
  PROJECT water_3_g3x3_ext
  RUN_TYPE MD
&END GLOBAL
&MOTION
  &CONSTRAINT
    &G3X3
      DISTANCES 1.8897268 1.8897268 3.0859239
      INTERMOLECULAR
      ATOMS 1 2 3
    &END G3X3
  &END CONSTRAINT
  &MD
    ENSEMBLE NVE
    STEPS 10
    TIMESTEP 2.5
    TEMPERATURE 298
  &END MD
&END MOTION
