energy drift in NPT MD simulation

[satya]

Hi,
  I am performing ab initio  NPT simulations for periodic system. After few 
MD  steps, the energy became positive suddenly.

 ENERGY| Total FORCE_EVAL ( QS ) energy (a.u.):           
 -7812.764025930553544
 ENERGY| Total FORCE_EVAL ( QS ) energy (a.u.):           
 -7812.749294149502930
 ENERGY| Total FORCE_EVAL ( QS ) energy (a.u.):           
 -7812.676524229716961
 ENERGY| Total FORCE_EVAL ( QS ) energy (a.u.):           
 -7811.995024580804966
 ENERGY| Total FORCE_EVAL ( QS ) energy (a.u.):           
 -7797.831216821386079
 ENERGY| Total FORCE_EVAL ( QS ) energy (a.u.):           
 -7551.236735853759455
 ENERGY| Total FORCE_EVAL ( QS ) energy (a.u.):           
 17791.55084644478847

 I enclosed my input below. Could you please suggest possible ways to 
rectify it.    

&FORCE_EVAL
  METHOD Quickstep

  &DFT
  BASIS_SET_FILE_NAME  /home1/bala/cp2k/tests/QS/BASIS_MOLOPT
  POTENTIAL_FILE_NAME  /home1/bala/cp2k/tests/QS/GTH_POTENTIALS
    CHARGE = 0
    &MGRID
      CUTOFF 350
      NGRIDS 5
      REL_CUTOFF 50 
    &END MGRID
    &QS
      METHOD GPW
      EPS_DEFAULT 1.0E-11
    &END QS
    &SCF
      SCF_GUESS RESTART  
      EPS_SCF 1.0E-7
      MAX_SCF 50 
      CHOLESKY OFF
      &OT 
       MINIMIZER DIIS  
       PRECONDITIONER FULL_ALL
       ENERGY_GAP 0.001
#       STEPSIZE 0.05
      &END OT
      &OUTER_SCF
       EPS_SCF 1E-7
       MAX_SCF 150
      &END OUTER_SCF     
    &END SCF
    &XC
     &XC_FUNCTIONAL PBE
      &END XC_FUNCTIONAL
        &vDW_POTENTIAL
         POTENTIAL_TYPE  PAIR_POTENTIAL
         &PAIR_POTENTIAL
          TYPE DFTD3
        PARAMETER_FILE_NAME  /home1/bala/cp2k/tests/QS/dftd3.dat
        REFERENCE_FUNCTIONAL PBE
        REFERENCE_C9_TERM .TRUE.
        CALCULATE_C9_TERM .TRUE. 
         R_CUTOFF 25.0
       &END PAIR_POTENTIAL
      &END vDW_POTENTIAL
       &XC_GRID
        XC_DERIV  SPLINE2
        XC_SMOOTH_RHO NN50
      &END XC_GRID
   &END XC
  &END DFT

  &SUBSYS
    &CELL
      ABC 21.8620 16.2099 43.6020
      ALPHA_BETA_GAMMA 90.0 92.7540 90.0
     &CELL_REF
      ABC 22.8620 17.2099 44.6020
      ALPHA_BETA_GAMMA 90.0 126.0 90.0
     &END CELL_REF
    
    &END CELL

    &COORD
     @INCLUDE coor.xyz  
    &END COORD

    &KIND H
      BASIS_SET DZVP-MOLOPT-SR-GTH
      POTENTIAL GTH-PBE-q1
    &END KIND

    &KIND C
      BASIS_SET DZVP-MOLOPT-SR-GTH
      POTENTIAL GTH-PBE-q4
    &END KIND

    &KIND N
      BASIS_SET DZVP-MOLOPT-SR-GTH
      POTENTIAL GTH-PBE-q5
    &END KIND
    &KIND O
      BASIS_SET DZVP-MOLOPT-SR-GTH
      POTENTIAL GTH-PBE-q6
    &END KIND

    &KIND Fe
      BASIS_SET DZVP-MOLOPT-SR-GTH
      POTENTIAL GTH-PBE-q16
    &END KIND
    &KIND Zn
      BASIS_SET DZVP-MOLOPT-SR-GTH
      POTENTIAL GTH-PBE-q12
    &END KIND

    &KIND Cd
      BASIS_SET DZVP-MOLOPT-SR-GTH
      POTENTIAL GTH-PBE-q12
    &END KIND
  &END SUBSYS
  STRESS_TENSOR ANALYTICAL
&END FORCE_EVAL

&GLOBAL
  PROJECT OUT-GEO-OPT
  RUN_TYPE MD
  PRINT_LEVEL MEDIUM
&END GLOBAL

&MOTION
  &MD
  ENSEMBLE NPT_F
  STEPS 10000
  TIMESTEP 0.5
  TEMPERATURE 195.0
  &BAROSTAT
   PRESSURE 1.0
   TIMECON [wavenumber_t] 4000.
   &THERMOSTAT
    TYPE CSVR
   &END THERMOSTAT
  &END BAROSTAT
  &THERMOSTAT
     TYPE NOSE
     REGION GLOBAL
     &NOSE
       TIMECON [wavenumber_t] 4000.0
       LENGTH  3
       YOSHIDA 3
       MTS 2
      &END NOSE
    &END THERMOSTAT
 &END MD
 &PRINT
    &RESTART
      LOG_PRINT_KEY T
        &EACH
          MD 50 
        &END EACH
      ADD_LAST NUMERIC
    &END RESTART
    &TRAJECTORY
      LOG_PRINT_KEY T
        &EACH
          MD 1 
        &END EACH
      ADD_LAST NUMERIC
    &END TRAJECTORY
    &VELOCITIES
      LOG_PRINT_KEY T
        &EACH
          MD  1 
        &END EACH
       ADD_LAST NUMERIC
    &END VELOCITIES
  &END PRINT
&END MOTION


#&EXT_RESTART
#    RESTART_FILE_NAME OUT-GEO-OPT-1.restart
#&END EXT_RESTART

Thank you..
Satyanarayana B
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