Help on adding limit potential to do AIMD simulation in CP2K

[horin cham]

Dear all,

I wanted to do a simulation of water molecules inducing catalyst surface remodeling, so I wanted to implement the addition of a limiting potential to bring water molecules close to the catalyst surface, leading to catalyst surface remodeling.

This was done by referring to the SI section of this literature (doi.org/10.1021/acscatal.8b01232) 

I have set the limiting potential in the inp file as follows. Where 1-141 is specified for all atoms in the water molecule, Z0 is taken as the z-value of the catalyst surface, and B is approximated by the calculation of the reference formula.

  &EXTERNAL_POTENTIAL
    ATOMS_LIST 1..141
    FUNCTION -1 * (1 - ((Z - Z0) / B)^12) / (1 - ((Z - Z0) / B)^24)
    VALUES [eV] 0.20 [angstrom] 5.0
    PARAMETERS B Z0
  &END EXTERNAL_POTENTIAL
&END FORCE_EVAL

Running 2.7ps with NVT resulted in some of the water molecules going up and some going down, and no dissociation of the water molecules was found to occur. So, my question is : 1.Does this mean that the effect of the catalyst (Cu2O) surface on the adsorption of water molecules is stronger than the effect of the confining potential (i.e., running NVT without confining potential also gives this result, and adding confining potential is not very useful?) 2. What should I do if I want all water molecules above the vacuum layer to be close to the catalyst surface, or even if water dissociation occurs?

Your help would be greatly appreciated!

All the best,

chorin.