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Re: [lammps-users] [EXTERNAL] Re: Inquiry on mu-P-T ensemble
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Re: [lammps-users] [EXTERNAL] Re: Inquiry on mu-P-T ensemble


From: "Thompson, Aidan" <athomps@...3...>
Date: Thu, 12 Apr 2018 16:10:30 +0000

Yes mu-p-T is not a thermodynamic ensemble. However, LAMMPS does not forbid it. There are two problems:

1. This combination has not been tested *at all*
2. There is no fixed extensive quantity (N or V or E), so the system is free to grow or shrink with any constraint.  

However, if you introduced a second species that is not exchanged, you can run mu1-N2-p-T dynamics. This is a thermodynamic ensemble, and can be used to study polymer swelling, etc. It does not suffer from Problem 2, but Problem 1 is still a concern.

Aidan


--
      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
-----Original Message-----
From: Wahab Mirco <Mirco.Wahab@...5409...>
Date: Thursday, April 12, 2018 at 3:56 AM
To: lammps/lammps LAMMPS Users List <lammps-users@lists.sourceforge.net>
Subject: [EXTERNAL] Re: [lammps-users] Inquiry on mu-P-T ensemble

    On 12.04.2018 11:32, MASATO KOIZUMI wrote:
    
    > Hello. Just following up, I was curious if LAMMPS could perform a 
    > mu-P-T, i.e. constant chemical potential, constant pressure and constant 
    > temperature. I am planning to create a dynamic simulation where 
    > molecules are inserted into the simulation box under isobaric and 
    > isothermal conditions. I would like to have the volume of the simulation 
    > box change.
    
    A µ-P-T ensemble isn't a real thermodynamical ensemble. You can figure
    that out if you consider the relation of µ and P in an ideal gas.
    (https://en.wikipedia.org/wiki/Gibbs%E2%80%93Duhem_equation)
    
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