How to make a ratio for separation of N2/CO2 mixture

LAMMPS LAMMPS General Discussion
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1

Dear All,

I will try to calculate N2/CO2 selectivity for CO2 capture in MOF. I would like to compute gcmc in lammps for CO2 capture. Do you know how to make a ratio of molecule? For instance, I will give a CO2 to N2 molar ratio of 15 to 85. Should I change molar chemical potential because of this ratio?

If I change pressure, should I change molar chemical potential as well?

2

If you do GCMC, you are fixing the chemical potential, and therefore you can’t pick the number of molecules as well. It’s either one or the other.

Simon

3

What is your suggestion to make a ratio? I am quite a new user on LAMMPS.

4

If you want to set the number of molecules, then just create the number of molecules you want. Your chemical potentials and pressure are not going to be controled though.

5

Thanks a lot for answer. I prefer to give a certain pressure, like 0.1 atm, and temperature (298.15 K). The system can control the number of molecules depending on a ratio (15:85). What is the command for it?

6

Is there any example for gas mixture to calculate selectivity of gases? I found some examples for just one gas like Water adsorption in silica -

7

Are you aware of a Monte Carlo method that allows enforcing a strict molecule ratio? I’m not. In typical GCMC, you fix the chemical potentials (or partial pressures), and the composition results from that. LAMMPS won’t let you fix both the molecule numbers and the chemical potential at the same time, that wouldn’t make thermodynamic sense.

8

It’s not very different to have two species; you just need to use two GCMC commands. I think you don’t see many examples of such GCMC applications because there are faster codes than LAMMPS for GCMC, and people tend to perform these types of calculations using other software like GOMC or RASPA.

9

We will look at the Working Capacity, Isosteric Adsorption Heat (QST) and Selectivity (S) quantities to be obtained by simulating real operating conditions for N2, CO2 and H2O gas mixtures using MOF5. Can I make this in Lammps?

Actually, RASPA is too slow because it runs serially with one core. So I do not prefer to use RASPA. But I do not know GOMC.

10

Yes of course, but not the way you are trying to.

No, RASPA is a true monte carlo code and is way faster than LAMMPS for GCMC, particularly since RASPA 3.