Author Topic: How to eliminate the boundary effect in GEMC simulations?  (Read 143 times)

Jianbo

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How to eliminate the boundary effect in GEMC simulations?
« on: November 25, 2020, 04:24:53 AM »
Dear RASPA users,

I want to simulate the adsorption of water on zeolites via Gibbs ensemble Monte Carlo (GEMC) simulation.

In a Grand Canonical Monte Carlo (GCMC) simulation, I can create a free space of several hundred Å to eliminate the effect.

However, it seems impractical to do the same in a GEMC simulation.

Thus, how can I eliminate the influence of image zeolites on water?

Thanks in advance
Sincerely,
Jianbo Wang

David Dubbeldam

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Re: How to eliminate the boundary effect in GEMC simulations?
« Reply #1 on: November 28, 2020, 08:10:49 PM »
Boundary effects are already eliminated in the grand-canonical and Gibbs approach.
For the grand-canonical approach, only the adsorbed phase is simulated.
For the Gibbs approach, the adsorbed phase and a fluid phase is simulated.
In both there are no surface effects. You do need sufficiently large systems to minimize finite-size effects.

Jianbo

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Re: How to eliminate the boundary effect in GEMC simulations?
« Reply #2 on: December 08, 2020, 11:53:09 AM »
Dear Dubbeldam,

Thanks for your reply. It seems I misused the two effects, i.e. the boundary effect and the finite-size effect.

In the grand-canonical approach, the intermolecular force between the substrate of interest and the image substrate can be minimized by creating the free space in the z-direction. In other words, the finite-size effect can be handled.

However, for the Gibbs approach,  if the simulation box of the adsorbed phase is enlarged to avoid the finite-size effect, a fluid phase seems to appear in this simulation box.

So, is it practical to set the adsorbed phase box with a sufficiently large box volume?

Thanks in advance
Sincerely,
Jianbo Wang

David Dubbeldam

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Re: How to eliminate the boundary effect in GEMC simulations?
« Reply #3 on: December 23, 2020, 09:20:53 PM »
Do you mean that you want to simulate adsorption on the outside of the zeolite?
Because using the grand-canonical approach only the adsorbed phase inside the framework is computed.

I have no experience with adsorption on the external surface of a zeolite.