[CP2K:1386] EMAX_SPLINE too small

Laino Teodoro teodor... at gmail.com
Thu Oct 2 09:45:37 UTC 2008

... and now most important few comments on your input file:

>   &MM
>       &CHARGE
>         ATOM Si
>         CHARGE 2.7226
>       &END CHARGE
>       &CHARGE
>         ATOM O
>         CHARGE -1.3613
>       &END CHARGE
>       &SHELL O
>         CORE_CHARGE 1.91981
>         SHELL_CHARGE -3.28111
>         MASS_FRACTION 0.1
>         SPRING [eV*angstrom^-2] 256.71027
>         MAX_DISTANCE [angstrom] 1.0
>       &END SHELL

don't you see anything strange from the charge balance of your system???
So .. you have a Si atom which has a charge of 2.7226
and an oxygen which has a charge of -1.3613.
SiO2 must be neutral.. unless you don't do some exotic type of SiO2.
Let's assume for the moment that you do the standard SiO2.
So the balance of charge is 0= 2.7226-2*1.3613 without considering  
the contribution of

Strange enough you put then a core-shell on the oxygen with the  
following charges:
CORE    1.91981
SHELL   -3.28111

the core-shell gives an additional charge on the O atom of -1.3613..
So.. can you explain me what are you simulating?
SiO2 with your settings has a charge of -1.3613

Think about it....
Maybe you want to set the charge of O to zero and keep the charge  
coming from the core-shell...
It must be you to fix this controversial settings!

>       &EWALD
>         EWALD_TYPE spme
>         ALPHA 0.4
>         GMAX 61 61 61 ! just for trying
>        !O_SPLINE 2
>       &END EWALD
>   &END MM
>     &CELL
>       ABC 14.4 14.4 14.4
>     &END CELL

a mesh of 61x61x61 for 14 angstrom box is maybe a bit exaggerated!
why do you want to have such an accuracy on the electrostatic and keep
the spline accuracy to 10^-6 - 10^-7.. ??

Think about it...

>   &MD
>     STEPS 1000
>     TIMESTEP 0.2

TIMESTEP of 0.2 is already a quite good setting.. BUT... keep in mind  
that the core-shell may require even smaller integration time steps,
due to the high frequency of the core-shell model..
It's up to you to check that you have a properly conserved total  
energy in your simulation...


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