In Lammps Manual (v13Apr 2017), the fix gcmc command, the Syntax section, it said that:
“mu = chemical potential of the ideal gas reservoir (energy units)”
Then, in the Description section , it said this :
“ The chemical potential is a user-specified input parameter defined as:
μ=μ_id + μ_ex ”
(1)The Question is : does “chemical potential of the ideal gas reservoir” mean: the chemical potential of the “ideal gas” reservoir, or the “ideal” gas reservoir ? Which value I’m supposed to choose: μ,μ_id, or μ_ex ?
(2)
Through Widom’s Test Particle Insertion method, I got a value of = -23.33 KJ/mol of water, which is comparable to the excess chemical potential of -22.8 KJ/mol in Agarwal et al.(2014)[1] ’s work.
Corti (1998) [2] also stated that:
“Widom [1, 2] showed that the excess chemical potential μex of a system of N interacting particles is given by
μex = - kT ln< exp(- φ/kT)>N”
So the Question is : from Widom’s Test Particle Insertion method, I got the excess chemical potential, could this excess chemical potential be used in ficx gcmc represent the mu value ?
[1] Agarwal, A.; Wang, H.; Schütte, C.; Site, L. D. Chemical potential of liquids and mixtures via adaptive resolution simulation. The Journal of chemical physics 2014, 141 (3), 034102.
[2] Corti, D. S. Alternative derivation of Widom’s test particle insertion method using the small system grand canonical ensemble. Molecular Physics 1998, 93 (3), 417-420.