[CP2K-user] Water-bilayer/Metal interface - Ab intio MD

[Anna Anic]

Hey everybody,

I am trying to do Ab-initio MD for a metal-water interface. I am using a 
symmetric slab and positioned a bilayer of water at both surface sites. 
Now, if I run the simulation my water layer just decomposes into the vacuum 
region. That is why I would like to implement an vacuum potential barrier 
at some point in the z-direction to prevent my water from just "flying 
away".
I tried using the &EXTERNAL_POTENTIAL keyword and defined a harmonic 
function as a barrier.
But when I run the simulation the hydrogen atoms from the H2O-bilayer  are 
"blown away".
The question is, what did I do wrong? Is the idea legit? Does anyone have a 
proposal how to fix the problem or how to do it differentey.

Greetings,

Anna

(I attached my input file,geometry and trajectory )
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