[lammps-users] Fixing the Graphene sheet

Hii all,

I am studying the adosrption on graphene surface, how can i fix the graphene sheet so that it cannot move during MD run.

Regards
Javed

You can put the graphene on a substrate like this paper:

https://iopscience.iop.org/article/10.1088/0022-3727/46/20/205303/pdf

Dar Javeed <[email protected]> 于2021年11月25日周四 下午1:52写道:

Hi Javed
Why fixing it, if you are studying adsorption on a free standing graphene sheet.
This choice is matter of the real problem you have to solve.
2D pbc can be a solution. If deposition is directional, cancelling induced drift motion can be done using fix momemtum command, etc.
Best
Pascal

You can put the graphene on a substrate like this paper:

https://iopscience.iop.org/article/10.1088/0022-3727/46/20/205303/pdf

Dar Javeed <[email protected]> 于2021年11月25日周四 下午1:52写道:

You can simply omit the graphene sheet particles from the integrator, i.e. something like:

group everything_else subtract all graphene
fix integrate everything_else nvt 300 300 100 etc etc

Cheers,
Shern

Yes, if the graphene atoms motion induced by adsorbing atoms can be neglected : ie at very low impinging kinetic energy.
I think first identifying/understanding what the problem to solve is, and then going to translation into a MD modeling with the relevant approximations for «realistic » simulations.
Best

LAMMPS by default calculates all forces. All forces by the graphene sheet on other particles will be calculated and applied to those particles.

But by using “fix nvt” on only the other particles, only those particles’ positions will be updated, while the graphene sheet particles’ positions won’t be updated – i.e., they won’t move.

I agree with Pascal that you need to be sure that the physics you are intending to simulate is not affected by making the graphene sheet immobile – but once you are sure that you want the sheet to be immobile, this is the simplest way to do it.