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I want to run molecular dynamics with LAMMPS, the aim is to simulate a platinum surface with a gas phase consisting of simple molecules. I would like to use periodic boundary conditions in order to create a bulk-like behaviour for the gas phase. However, I'm not sure how to place the surface, I see two obvious options:

  1. I place the surface at the middle of the simulation box (It will split the simulation box in two then) and ask for PBCs in all the directions of the space.
  2. I place the surface at the bottom of the simulation box and remove the periodicity along the axis perpendicular to the surface and constrain it to stay there.

The first option seems to be the best but requires the surface to be thick enough. The second option is less physical as one direction is not well represented and constraints are applied. I still have doubt because for ab-initio calculations (Single points) I used to choose the second one.

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    $\begingroup$ If your are using PBC you are creating two surfaces one at top and other at bottom you can also use shrink wrap boundary condition, where only one part of surface will be expose to gases $\endgroup$
    – Pranav kumar
    Jul 10, 2021 at 6:12
  • $\begingroup$ Okano, was the last comment by Pranav helpful? Have you made any progress on this question? Is there any update you can give us? $\endgroup$
    – Nike Dattani
    Dec 27, 2021 at 4:09
  • $\begingroup$ This question has been closed as it seems to be abandoned. It can be reopened if someone wants to add an answer or the OP addresses questions/suggestions in the comments. $\endgroup$
    – Tyberius ♦
    Jan 4, 2022 at 15:27

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