Ask the building of air or specific gas environment

[jeong9090]

Hi,

I'm VNL user and working on thermal transport.

I wonder whether I can make air or specific gas environment with VNL.

I made graphene on Cu substrate. There is a gap between graphene and Cu.

I know that there is vacuum gap between graphene and Cu when I build this structure by VNL.

Can I apply air or a specific gas(ex. N2 molecules) environment in this gap when I build this structure by VNL?

I want to compare vacuum condition with air condition when I calculate heat transfer between graphene and Cu with MD.

I'd really appreciate it if you give me any comments.

Thanks,

Jaeyoung Jeong

[Petr Khomyakov]

Do you just mean that you would like to have some foreign atoms or molecules at the graphene-Cu interface? You can do it in QuantumATK in several ways.

One way would be to first put the molecules on top of the Cu surface in same way and do ion relaxation to allow the molecules to relax to their equilibrium positions on the surface,  and then place a graphene sheet on top of the contaminated surface of Cu. After that you would need to do geometry optimization of the interface structure in the same, I suppose, you did for the clean interface.

[jeong9090]

Hi, Petr Khomyakov

Yes, I did the clean interface.

As you mentioned, I want some foreign atoms or molecules at graphene-Cu interface.

This is because graphene was physically transferred on the Cu substrate in my experiment.

I suspect that there may be the air gap between graphene and Cu because I did not heat my sample.

I already finished the vacuum condition which means the clean Cu surface.

If I'm followed by your direction, can I export the final structure ( graphene/gap having gas molecules/Cu) to LAMMPS data file?

Thanks,

Jaeyoung Jeong

[Petr Khomyakov]

If I'm followed by your direction, can I export the final structure ( graphene/gap having gas molecules/Cu) to LAMMPS data file?

Yes, you can do it, see https://docs.quantumwise.com/tutorials/vnl_import_export_files/vnl_import_export_files.html and https://docs.quantumwise.com/tutorials/lammps_trajectories/lammps_trajectories.html.

[jeong9090]

Hi,

I have a question to make a N2 molecule.

Nitrogen is N2 in air not N.

When I want to make N2 molecule, how to define the bonding between N and N?

Thanks,

Jaeyoung

[Petr Khomyakov]

You have to start from some decent guess for the N-N separation distance, and do separation distance relaxation (geometry optimization) using, e.g., LCAO or PW QuantumATK-Calculator, see the tutorial https://docs.quantumwise.com/tutorials/geometry_optimization/geometry_optimization.html.