&FORCE_EVAL
  METHOD FIST
  &MM
    &FORCEFIELD
      parm_file_name ../sample_pot/pot_bond.pot
      parmtype CHM
    &END FORCEFIELD
    &POISSON
      &EWALD
        EWALD_TYPE spme
        ALPHA .44
        GMAX 24
        O_SPLINE 6
      &END EWALD
    &END POISSON
  &END MM
  &SUBSYS
    &CELL
      ABC 24.955 24.955 24.955
    &END CELL
    &TOPOLOGY
      CHARGE_O
      COORD_FILE_NAME ../sample_pdb/butane.pdb
      COORDINATE pdb
    &END TOPOLOGY
  &END SUBSYS
&END FORCE_EVAL
&GLOBAL
  PROJECT pot_bond
  RUN_TYPE md
&END GLOBAL
&MOTION
  &MD
    ENSEMBLE NVE
    STEPS 1
    TIMESTEP 0.5
    TEMPERATURE 298
  &END MD
&END MOTION