Apply external force on a slab system

[Nam Tran]

Dear CP2K users and experts.

I am trying to simulate the interaction of a surface with a liquid layer under a high pressure using ab initio molecular dynamics. The system is illustrated in the figure below (I have some specific reasons that I need to use vacuum). In order to apply the load to the top slab an external force acting on the layer is needed. 

I found in the tutorial by Prof. Marcella (https://www.cp2k.org/exercises:2015_cecam_tutorial:mtd1) using external potential (CP2K_INPUT / FORCE_EVAL / EXTERNAL_POTENTIAL) to constrain the motion of molecules. From my understanding the external potential will act on each atom with a force of F=-dE/dr. So my idea is using the command to setup a constant external force to the top atomic layers.

&EXTERNAL_POTENTIAL
      ATOMS_LIST   1..20
      FUNCTION (A/B)*Z
      PARAMETERS A B
      UNITS [eV] [angstrom]
      VALUES 0.5 1.0
&END EXTERNAL_POTENTIAL

That would applied a constant normal (along z direction) force of 0.5 eV/A (this value is chosen randomly) to the chosen atoms. I wonder if the above setting will work?

Please correct me if I have some misunderstanding. 

I appreciate any advises and recommendations.

Regards

Nam

[mdsimula...@gmail.com]

Hello,

Were you able to test these settings?  If so, did it work?

Thanks!