[CPMD-list] CPMD/GROMOS96 quantum box sizes

[Ute Roehrig]

Hi Ian,

can you send me one complete output file, where this cell size problem
occured? It sounds like a resurrecting bug in the QM/MM code...

Ute

--
************************************************
                  Ute Roehrig
************************************************
Lab. of Computational Chemistry and Biochemistry
EPFL BCH 4122
CH-1015 Lausanne
Phone +41-(0)21-693 0324
Fax   +41-(0)21-693 0320
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On Thu, 9 Sep 2004, Ian R. Greig wrote:

> Dear CPMD-users,
>
> I am trying to set up a small molecule-in-water simulation using the
> CPMD/GROMOS96 code of Roethlisberger et al. The small molecule is to be
> QM and the surrounding solvent MM. My starting coordinates have been
> generated using GROMOS96.
>
> I have successfully performed a wavefunction optmization and a geometry
> optimization using a minimally sized quantum cell (obtained by fiddling
> with the cell parameters until I do not get the...
>
>  WARNING!!!  Box too small in x direction
>  WARNING!!!  Box too small in y direction
>  WARNING!!!  Box too small in z direction
>
> ...messages in the output file.
>
> When I use the geometry optimized structure as a restart point for the MD
> run I start to get the `box too small` warning messages at each MD step.
>
> I have tried to increase the box size by upto 10 angstrom in all three
> dimensions and I still get the warning messages when I try to start the MD
> run (which procedes smoothly otherwise).
>
> My input file can be found below.
>
> Any thoughts would be greatly appreciated.
>
> Ian
>
>
> ! MD startup run
> ! Oxazolinium ion in box of 55 water molecules
> ! A minimum quantum box is used for this run
>
> &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
> SPLIT
> SAMPLE_INTERACTING
> 10
> GROMOS
> ADD_HYDROGEN
> 7
> 1 3 7 8 11 14 16
> &END
>
> &CPMD
> QMMM
> RESTART WAVEFUNCTION COORDINATES
> MOLECULAR DYNAMICS
> TEMPCONTROL IONS
> 341.0 30.0
> MAXSTEP
> 200
> TRAJECTORY SAMPLE
> 20
> TIMESTEP
> 4.0
> EMASS
> 600.0
> MEMORY BIG
> CONVERGENCE
> 1.0E-5  1.0E-4
> SPLINE POINTS
> 3000
> &END
>
> &SYSTEM
> ANGSTROM
> POISSON TUCKERMAN
> SYMMETRY
> 0
> CELL
> 18.6  0.918  0.789  0  0  0
> CUTOFF
> 70
> 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
> EXCHANGE CORRELATION TABLE NO
> FUNCTIONAL BLYP
> GC-CUTOFF
> 5.0E-06
> &END
>
>
>
>
>
> ------------------------------------------------------------------
>                           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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