Which barostats can be applied for non-cubic simulation boxes?
none at the moment. It’s on the to-do list.
Is the Lammps code able to calculate the Gibbs free energy of the system?
Not directly - my understanding is there is no 1 way to do this. We will soon release
some thermodynamic integration add-ons that do this for a particular kind of system.
I’m CCing a couple other LAMMPS developers if they want to comment.
Steve
You can construct an orthorhombic simulation cell corresponding to your hexagonal structure, and use fix npt/aniso to simulate your system.
The add-ons that Steve was talking about will enable you to compute the free energy difference between an ordered structure (solid) and a disordered structure. Once the add-ons have been released, you should be able to tailor them to allow you to compute the Gibbs free energy of your system (relative to a reference state).
Sai.