I have some doubts about commands “fix widom” and “fix gcmc”.
Only temperature parameter T is required in command “fix widom”, so how can I compute chemical potential in specified temperature and pressure through this command? How about “fix widom” + “fix npt”?
I notice the output from fix widom is a vector of length 3, and the first column is average excess chemical potential on each timestep. So can it be used as input parameter chemical potential mu in command “fix gcmc”?
These are very open-ended questions that touch on issues far outside the scope of LAMMPS. That said, here are some quick responses:
You are free to use fix widom with fix npt or any other fix you like. However, for the purposes of calculating chemical potential using Widom insertion, the difference between NVT and NPT is order O(1/N) i.e. not important. Given that, there is no good reason to use fix npt with fix widom.
No, excess chemical potential can not be used as input parameter chemical potential mu. mu is defined at the very top of the doc page as:
mu = chemical potential of the ideal gas reservoir (energy units)
This definition clearly indicates that mu is not the excess chemical potential.
These are very open-ended questions that touch on issues far outside the scope of LAMMPS. That said, here are some quick responses:
You are free to use fix widom with fix npt or any other fix you like. However, for the purposes of calculating chemical potential using Widom insertion, the difference between NVT and NPT is order O(1/N) i.e. not important. Given that, there is no good reason to use fix npt with fix widom.
No, excess chemical potential can not be used as input parameter chemical potential mu. mu is defined at the very top of the doc page as:
mu = chemical potential of the ideal gas reservoir (energy units)
This definition clearly indicates that mu is not the excess chemical potential.