From:  "Thompson, Aidan" <athomps@...3...> 
Date:  Fri, 13 Oct 2017 22:03:51 +0000 
There are a lot of complicating factors in your example. Also, it is gigantic. I can't check every possible thing you might be doing wrong. However, I did run my own tests on a modified version of in.gcmc.lj, in which I ran two gcmc fixes
with two LAMMPS types with identical interaction coefficients. The total density and pressure of the system came out slightly lower than for the 1component case, while the excess chemical potential came out slightly higher. I think is due to the fact the
ideal gas contribution to chemical potential is different by shifted by kTln(2) for 2component case. In any event, the numbers of types 1 and 2 are the same, within statistical noise.
 Aidan P. Thompson 01444 Multiscale Science Sandia National Laboratories PO Box 5800, MS 1322 Phone: 5058449702 Albuquerque, NM 87185 Fax : 5058457442 Email:athomps@...3... Cell : 5052181011 From:
"chenwei@...7134..." <chenwei@...7134...> Dear LAMMPS users, I try to perform grand canonical Monte Carlo simulation for binary mixture by LAMMPS.
I want a pure GCMC simulator. Firstly, I test the program by the simulation of one component hard sphere fluid. The cutoff distance of LJ 126 potential is set equal to sigma, it is not a perfect hard sphere system, but the density of the system from the simulation
is very close to the theoretical one. However, there is a problem when I do the simulation for a binary hardsphere mixture. The densities predicted by the simulator are always far away from the confirmed theoretical ones.
The GCMC exchange is performed by these two commands in my script:
fix 1 O gcmc 1 1 1 1 29494 $T 3.982254 0.1 group O The LAMMPS Version is (6 Jul 2017). Please find the full .in script and the .data file from the attachment.
Thank you very much, Wei

Attachment:
in.gcmc.lj2
Description: in.gcmc.lj2