[CP2K-user] Apply external force on a slab system
Nam Tran
trann... at gmail.com
Sun May 24 12:26:29 UTC 2020
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.
[image: Slide1.jpeg]
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
<https://manual.cp2k.org/trunk/CP2K_INPUT/FORCE_EVAL/EXTERNAL_POTENTIAL.html>*)
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
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