LAMMPS WWW Site - LAMMPS Documentation - LAMMPS Mailing List Archives
Re: [lammps-users] [EXTERNAL] how to perform grand canonical Monte Carlo simulation for binary mixture by LAMMPS?
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [lammps-users] [EXTERNAL] how to perform grand canonical Monte Carlo simulation for binary mixture by LAMMPS?


From: chenwei@...7134...
Date: Wed, 25 Oct 2017 09:05:50 +0800 (GMT+08:00)

Dear Aidan P. Thompson,


I fixed this problem by using two different random number seeds in those two commands:


fix                1 O gcmc 1 1 1 1 29494 $T 9.0 0.1 group O

fix                2 C gcmc 1 1 1 2 271828 $T 9.0 0.1 group C


Best wishes´╝î


Wei

-----Original Messages-----
From:"Thompson, Aidan" <athomps@...3...>
Sent Time:2017-10-14 06:03:51 (Saturday)
To: "chenwei@...7134..." <chenwei@...7134...>, "lammps-users@lists.sourceforge.net" <lammps-users@lists.sourceforge.net>
Cc:
Subject: Re: [EXTERNAL] [lammps-users] how to perform grand canonical Monte Carlo simulation for binary mixture by LAMMPS?

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 1-component 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 2-component 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: 505-844-9702

      Albuquerque, NM 87185     Fax  : 505-845-7442

      E-mail:athomps@...3... Cell : 505-218-1011

 

 

From: "chenwei@...7134..." <chenwei@...7134...>
Date: Tuesday, September 26, 2017 at 3:55 AM
To: lammps/lammps LAMMPS Users List <lammps-users@lists.sourceforge.net>
Subject: [EXTERNAL] [lammps-users] how to perform grand canonical Monte Carlo simulation for binary mixture by LAMMPS?

 

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 12-6 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 hard-sphere 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

fix                2 C gcmc 1 1 1 2 29494 $T 1.065682 0.1 group C

In addition, the density of the atoms handled by the second fix command is always close to zero. Here,  the density of group C is almost zero, but if I change the order of those two fix commands, then the density of group O is close to zero.

 

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

 




--
State Key Laboratory of Multi-Phase Complex Systems
Institute of Process Engineering (IPE)
Chinese Academy of Sciences (CAS)
P.O. Box 353, Beijing 100190, China
Tel: +86-10-8254 4839
Fax: +86-10-6255 8065
Email: chenwei
@ipe.ac.cn
Http://www.mpcs.cn/emms