MD simulation doesn't run very long

[andrew...@eas.gatech.edu]

Hi cp2k users,

I'm interested in doing some MD and metadynamics, so I looked at
cp2k.  We're having some problems though and I thought I would post to
see if anyone here knows what we might be doing wrong.  Thanks a lot!

Cheers,
Andrew

Here's my data:

I compiled cp2k using gfortran and it runs a test file someone gave us
seemingly okay.  We started out with a box of water that runs fine in
lammps but cp2k ran into some connectivity issues (cp2k doesn't seem
to find water molecules automatically across cell boundaries).  I
fixed this, by making certain the water molecules were all in the
image reference and defining the connectivity manually.  This didn't
fix that specific problem though: the symptom is that the simulation
runs for ~20-30 time steps and then the temperature increases
dramatically and we get some atoms crash:


 
*******************************************************************************
 ENSEMBLE TYPE
=                                              nvt
 STEP NUMBER
=                                               26
 TIME [FS]                    =
26.000000
 CONSERVED QNTY               =
-0.299834451059E+01

                                         INSTANTANEOUS        AVERAGES
 CPU [S]                      =
0.22                 0.39
 {E-E0}/{k_b*N_at}            =          0.396202120408E+02
0.335570376311E+01
 POTENTIAL ENERGY[hartree]    =         -0.549743589253E+01
-0.462863744377E+01
 KINETIC ENERGY[hartree]      =          0.249463138359E+01
0.153631845774E+01
 TEMPERATURE[K]               =
656.451              404.275
 
*******************************************************************************

 WARNING| Particles:     609    265 at distance [au]:     0.49549362
less than:      0.95400000; increase EMAX_SPLINE.

The temperature was supposed to be 300 K, but as you can see it blows
up the last few time steps.

Here is a link to the files:
http://shadow.eas.gatech.edu/~astack/water.tar.gz

Here is my input file, the commented out sections are different things
we tried to see if that made a difference.  The biggest thing that
seemed to affect the number of time steps was the options affecting
the spline.

&FORCE_EVAL
  METHOD FIST
  &MM
    &FORCEFIELD
!       &SPLINE
!               EMAX_SPLINE 1000.0
!               R0_NB [angstrom] 0.1
!       &END SPLINE
      &BEND
         ATOMS H O H
         KIND HARMONIC
         K [kcalmol*rad^-2] 120
         THETA0 [deg] 109.47
       &END BEND
       &BOND
         ATOMS O H
         KIND HARMONIC
         K [kcalmol*angstrom^-2] 500
         R0 [angstrom] 1.00
       &END BOND
      &NONBONDED
        &LENNARD-JONES
           ATOMS O O
           EPSILON [kcalmol] 0.1848
!           SIGMA [angstrom] 3.5532
           SIGMA [angstrom] 3.1655
           RCUT [angstrom] 10.0
         &END LENNARD-JONES
         &LENNARD-JONES
           ATOMS O H
           EPSILON [kcalmol] 0.0430
!           SIGMA [angstrom] 1.7883
           SIGMA [angstrom] 1.5932
           RCUT [angstrom] 10.0
         &END LENNARD-JONES
         &LENNARD-JONES
           ATOMS H H
           EPSILON [kcalmol] 0.0100
!           SIGMA [angstrom] 0.900
           SIGMA [angstrom] 0.8018
           RCUT [angstrom] 10.0
         &END LENNARD-JONES
      &END NONBONDED
    &END FORCEFIELD
    &POISSON
      &EWALD
        EWALD_TYPE ewald
        ALPHA 0.5
        GMAX 15
      &END EWALD
    &END POISSON
  &END MM
  &SUBSYS
    &CELL
      ABC 20 20 20
      UNIT ANGSTROM
      PERIODIC XYZ
    &END CELL
    &TOPOLOGY
        CONN_FILE_NAME water.psf
        CONNECTIVITY UPSF
        COORD_FILE_NAME water.pdb
        COORDINATE PDB
    &END TOPOLOGY
    &PRINT
      &TOPOLOGY_INFO HIGH
        FILENAME topology.inf
        PDB_INFO
        COMMON_ITERATION_LEVELS 1
        UTIL_INFO
        GENERATE_INFO
      &END TOPOLOGY_INFO
    &END PRINT
  &END SUBSYS
!  &RESCALE_FORCES
!    MAX_FORCE 0.001
!  &END
!  &PRINT
!       &FORCES
!         FILENAME water.force
!        &END FORCES
!  &END PRINT
&END FORCE_EVAL
&GLOBAL
  PROJECT water
  RUN_TYPE MD
!  PRINT_LEVEL HIGH
&END GLOBAL
&MOTION
  &MD
    ENSEMBLE NVT
    STEPS 300
    TIMESTEP 1
    TEMPERATURE 300
!    TEMP_TOL 1.0
   &THERMOSTAT
    &NOSE
      LENGTH 1
      YOSHIDA 3
      MTS 2
      TIMECON 500
    &END NOSE
   &END THERMOSTAT
   &PRINT
    &ENERGY HIGH
     EACH 1
    &END ENERGY
   &END PRINT
  &END MD
&END MOTION