[CP2K:1409] Force field for fully flexible water

Laino Teodoro teodor... at gmail.com
Tue Oct 7 21:38:49 UTC 2008

Dear Roger,

do you have an idea of what 353.0  kjmol*deg^-2  mean?
if you are at the equilibrium position, and you compress or enlarge  
the H-O-H angle of just one small irrelevant degree
the energy of your system would increase of ~ 85 kcal. This means  
that thermal fluctuations of few degrees normally connected with the
bending H-O-H would be enough to break chemical bonds.

That's why I'm not wondered to hear from you that your water is  
exploding!.. I'm not sure.. I had no time to test your input.. but the
result should be roughly like the famous Tsar bomb (if you're  
curious: http://www.youtube.com/watch?v=FfoQsZa8F1c )

Since I drunk few minutes ago a fresh glass of water (kindly offered  
from the Zurich water supply network), I can witness
that it was not like the plasma you call water! ;-)

So.. I would think a bit more on your units!

of course as Axel suggested, with a potential like this one.. maybe  
an integration time step of 0.05-0.1 fs is enough.. not for
getting a proper conserved quantity.. but at least to tame the  


>       &BEND
>         ATOMS H O H
>         K [kjmol*deg^-2] 353.0
>         THETA0 [deg] 109.4712
>       &END BEND

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