[EXTERNAL] Use of multiple fix gcmc commands

Dear lammps-users:

    I have two questions about using multiple fix gcmc commands to simulate binary gas adsorption:

    1\.When we simulate gcmc process of mixture, how to set the pressure and fugacity coefficient? 
       Should we set the pressure as partial pressure?  or just total pressure?
       Fugacity coefficient of components corresponding to partial pressure or total pressure, which one should be used?

It should be obvious that fix gcmc can only constrain the chemical potential/fugacity/fugacity coefficient/partial pressure of the specified component. The total pressure that results will depend on the amounts of the other components present.

   2\.Can we set specific composition of each component when we use multiple gcmc commands?
      For example,  I want to set the mol ratio of methane and butane as 0\.9/0\.1 in gas reservoir\. Is it possible to implement this with LAMMPS gcmc?

Any suggestion could help a lot. Thank you.

This is something you will have to figure out for yourself. A good starting point would be to assume ideal gas behavior, so the molar ratios of the components are equal to the fugacity ratios. If you want LAMMPS to automatically adjust one of the specified fugacities to achieve a particular mole ratio, you could try using fix controller command:


Adjusting the PID gains is non-trivial. Let me know if you get this to work :slight_smile: