&FORCE_EVAL
  METHOD FIST
  &MM
    &FORCEFIELD
      &spline
       rcut_nb 6.9
      &end
      parm_file_name ../sample_pot/charmm.pot
      parmtype CHM
      &CHARGE
        ATOM NH3
        CHARGE -1.14
      &END CHARGE
      &CHARGE
        ATOM HC
        CHARGE 0.38
      &END CHARGE
    &END FORCEFIELD
    &POISSON
      &EWALD
        EWALD_TYPE ewald
        ALPHA .5
        GMAX 21
      &END EWALD
    &END POISSON
  &END MM
  &SUBSYS
    &CELL
      ABC 13.858 13.858 13.858
    &END CELL
    &TOPOLOGY
      COORD_FILE_NAME ../sample_pdb/NH3.pdb
      COORDINATE PDB
    &END TOPOLOGY
  &END SUBSYS
&END FORCE_EVAL
&GLOBAL
  PROJECT nh3_4x6
  PRINT_LEVEL LOW
  RUN_TYPE MD
&END GLOBAL
&MOTION
  &CONSTRAINT
    &G4X6
      DISTANCES 1.9275 1.9275 1.9275 3.1483 3.1483 3.1483
      MOLECULE 1
      ATOMS 1 2 3 4
    &END G4X6
  &END CONSTRAINT
  &MD
    ENSEMBLE NVT
    STEPS 5
    TIMESTEP 2.5
    TEMPERATURE 298
    &THERMOSTAT
      REGION MOLECULE
      &NOSE
        LENGTH 1
        YOSHIDA 3
        TIMECON 500
        MTS 2
      &END NOSE
    &END
  &END MD
&END MOTION
