[CPMD-list] CPMD/GROMOS96 - maybe too much translation?

[Ian R. Greig]

Dear CPMD/GROMOS96 users,

I have a system consisting of one small molecule (approximately 30 atoms) 
and around 1000 water molecules that has been well-equilibrated (5 ns) 
using GROMOS96 in a periodic box that has dimensions that are 
approximately 3 nm x 3 nm x 3nm. 

I can successfully optimize the wavefunction using the code of 
Roethlisberger for the system in which the small molecule is treated QM 
and the water molecules are MM.

When I try and start an MD simulation the CPMD/GROMOS96 program exits with 
the 'maybe too much translation?' message.

Analysis of my GROMOS coordinate file shows that the positions of atoms 
in the x, y and z dimensions are within the approximate range on 0 - 3 nm 
and that the atom velocities have an appropriate distribution (cluster 
around zero with positive and negative values). 

I note that the CRD_INI.grm file generated by the code contains atomic 
positions that appear to display a range approximately double that of the 
original coordinates.

I have run the example file provided with the CPMD/GROMOS96 code 
distribution and that runs without problems: gromos.g96, CRD_INI.grm and 
CRD_FIN.grm all display similar distributions in x, y and z dimensions and 
the velocities are reasonably distributed.

I have tried both reading in the atomic velocities and also generating 
them from a Boltzman distribution.

I have attached the CPMD and GROMOS96 input files that I am using below.

Any insight into this problem would be much appreciated,

Ian


CPMD input file:

-----------------------------------------------------------------------

&QMMM
TOPOLOGY
topol.gr
COORDINATES
coord.gr
INPUT
input.gr
LONG RANGE ELECTROSTATIC COUPLING
RCUT_NN
8.0
RCUT_MIX
8.0
RCUT_ESP
8.0
SAMPLE_INTERACTING
10
GROMOS
ADD_HYDROGEN
7
1 3 7 8 11 14 16
&END

&CPMD
QMMM
QUENCH BOELECTRONS
RESTART WAVEFUNCTION COORDINATES
MOLECULAR DYNAMICS CP  
TEMPCONTROL IONS    
341.0 50.0  
MAXSTEP    
200  
TRAJECTORY SAMPLE    
20  
TIMESTEP    
4.0  
EMASS    
400.0
CONVERGENCE
1.0E-5  1.0E-4
SPLINE POINTS
3000
&END

&SYSTEM
ANGSTROM
POISSON TUCKERMAN
SYMMETRY
0
CELL
16  1.345  0.942  0  0  0
CUTOFF
10
CHARGE
+1
&END

&ATOMS
*H_GIA_BLYP KLEINMAN-BYLANDER
LMAX=S
4
5 10 13 18 
*H_GIA_BLYP KLEINMAN-BYLANDER ADD_H
LMAX=S
10
*N_MT_GIA_BLYP KLEINMAN-BYLANDER
LMAX=P
1
4
*C_MT_GIA_BLYP KLEINMAN-BYLANDER
LMAX=P
8
1 3 6 7 8 11 14 16
*O_MT_GIA_BLYP KLEINMAN-BYLANDER
LMAX=P
5
2 9 12 15 17
&END

&DFT
  NEWCODE
  FUNCTIONAL BLYP
  GC-CUTOFF
  1.0E-06
&END

-----------------------------------------------------------------

GROMOS96 input file:

TITLE
Oxazolinium ion in a box of water molecules
END
SYSTEM
#      NPM      NSM 
         1        0
END
START
#      NTX     INIT       IG     TEMPI       HEAT  NTXO        BOLTZ
         2        4   210185     341.0        0.0     1   8.31441E-3    
END
STEP
#   NSTLIM         T        DT
        10       0.0     0.002
END
BOUNDARY
#      NTB    BOX(1)    BOX(2)    BOX(3)      BETA  NRDBOX
         1       0.0       0.0       0.0      90.0       1
END
SUBMOLECULES
#     NSPM  NSP(1.. NSPM)
         1   3285 
END
TCOUPLE
#      NTT     TEMP0      TAUT
         0     341.0       0.1
         0     341.0       0.1 
         0     341.0       0.1
END
CENTREOFMASS
#   NDFMIN      NTCM       NSCM
         0         0    1000000  
END
PRINT
#     NTPR      NTPL      NTPP
         1       100         0
END
SHAKE
#      NTC       TOL
         1    0.0001 
END
FORCE
#      NTF array
# bonds    angles    imp.     dihe     charge nonbonded
# H        H         H        H
  1  1    1  1      1  1     1  1     1  1
# NEGR    NRE(1)    NRE(2)    ...      NRE(NEGR)
   1  3285 
END
PLIST
#     NTNB      NSNB     RCUTP     RCUTL
         1        10         1         1
END
LONGRANGE
# EPSRF     APPAK      RCRF
   50.0       0.0    0.7E10
END
LATSUM
  2   32   32   32   0   0.80000   1.33   100000
END





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                          Ian R. Greig

Chemistry Department                   Room 209, Green College
Room E257 2036 Main Mall               6201 Cecil Green Park Road
Vancouver, British Columbia            Vancouver, British Columbia
CANADA V6T 1Z1                         CANADA V6T 1Z1
Tel: + 1 604 822 4626                  Tel: + 1 604 221 1971
Fax: + 1 604 822 2847

irg20 at cantab.net
irg20 at chem.ubc.ca
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