[CP2K:211] no convergence blues with bulk sio2

[Matthias Krack]

Hello Axel,

I guess your problem is caused by the Si basis set you are using. The Si 
TZVP-GTH basis set from GTH_BASIS_SETS is well suited for molecular 
silicon compounds, but this basis set is not a proper choice for a 
condensed phase system like liquid silicon. The smallest exponent of 0.04 
will certainly cause trouble. I suggest to use a confined basis sets for 
such systems. In fact, the following Si basis set, which we are using

Si DZVP-GTH-confined
  2
  3  0  1  4  2  2
          1.22833188     0.32244243     0.00000000     0.05946364     0.00000000
          0.55019735    -0.13601264     0.00000000    -0.21026641     0.00000000
          0.21048366    -0.72541938     0.00000000    -0.51333658     0.00000000
          0.09122301    -0.34824798     1.00000000    -0.41087712     1.00000000
  3  2  2  1  1
          0.27500000     1.00000000

seems to work fine for liquid Si and SiO2. However, in case your choice 
was intented you have to resort to the techniques already suggested in the 
previous replies, but, anyway, these runs will most likely become very 
painful.

cheers,

Matthias


On Fri, 3 Aug 2007, Axel wrote:

> 
> hi all!
> 
> the following input fails to converge (either with OT set to ON or
> OFF).
> the exact same setting work very nicely with bulk h2o...
> does anybody have an idea where the problem could be?
> 
> &GLOBAL
>   FFTLIB FFTW3
>   PROJECT sio2-liq-qs
>   RUN_TYPE MD
>   PRINT_LEVEL LOW
> &END GLOBAL
> 
> &MOTION
>   &MD
>     ENSEMBLE NVE
>     STEPS 1000
>     TIMESTEP 0.2
>     TEMPERATURE 4000.0
>     TEMPERATURE_TOLERANCE 100.0
>   &END MD
>   &PRINT
>     &TRAJECTORY
>     &END TRAJECTORY
>     &VELOCITIES OFF
>     &END VELOCITIES
>   &END PRINT
> &END MOTION
> 
> &FORCE_EVAL
>   METHOD QS
>   &DFT
>     CHARGE 0
>     BASIS_SET_FILE_NAME GTH_BASIS_SETS
>     POTENTIAL_FILE_NAME GTH_POTENTIALS
>     &MGRID
>       CUTOFF 300
>     &END MGRID
>     &QS
>       WF_INTERPOLATION ASPC
>       EXTRAPOLATION_ORDER 3
>     &END QS
>     &SCF
>       SCF_GUESS ATOMIC
>       EPS_SCF      1.0E-6
>       MAX_SCF       30
>       WRITE_RESTART_EACH 0
>       &OT OFF
>         MINIMIZER DIIS
>         N_DIIS  7
>       &END OT
>       &OUTER_SCF
>         EPS_SCF 1.0E-6
>         MAX_SCF 5
>       &END
>     &END SCF
>     &XC
>       &XC_FUNCTIONAL PBE
>       &END XC_FUNCTIONAL
>       &XC_GRID
>         XC_SMOOTH_RHO NN50
>         XC_DERIV NN50_SMOOTH
>       &END
>     &END XC
>   &END DFT
>   &SUBSYS
>     &CELL
>       ABC 14.257800 14.257800 14.257800
>       UNIT ANGSTROM
>     &END CELL
>     &TOPOLOGY
>       COORDINATE PDB
>       COORD_FILE_NAME sio2-liq.pdb
>     &END
>     &KIND Si
>       BASIS_SET TZV2P-GTH
>       POTENTIAL GTH-PBE-q4
>     &END KIND
>     &KIND O
>       BASIS_SET TZV2P-GTH
>       POTENTIAL GTH-PBE-q6
>     &END KIND
>   &END SUBSYS
> &END FORCE_EVAL
> 
> 
> > 
> 

Dr. Matthias Krack
Computational Science
Department of Chemistry and Applied Biosciences
ETH Zurich
USI-Campus, via G. Buffi 13
6900 Lugano
Switzerland

Phone: +41 (0)58 666 48 05 (direct)
       +41 (0)58 666 48 00 (secretary)
Fax:   +41 (0)58 666 48 17

Email: kr... at phys.chem.ethz.ch
URL:   http://www.phys.chem.ethz.ch