[Wien] Chemical potental

[Víctor Luaña Cabal]

On Fri, Jan 30, 2015 at 05:50:58PM +0000, Mohammed Abujafar wrote:
> Dear Wien2k users and developers,Hi,How can I calculate the chemical
> potential using WIEN2k code?Any help will be appreciated.With best
> regardsMohammed

Mohammed,

The chemical potential has MANY definitions so is kind of
ambiguous.

For your purpose the chem pot is the Gibbs function per mol, g=G/n.
This equation is your objective:

   G(N,p,T) = U(N,V,E) - pV + TS

where U is the internal energy, for our purpose equivalent to the
quantum mechanical energy of your crystal (computed wwith wien2k),
p is the pressure (a parameter in this description), T the absolute
temperature (also a parameter).

The pV is easy theoretically: the pressure is a parameter and the volume,
V, should be known for you to do a calculation. If you have problems with
that part learn some crystallography.

The TS is more complex. I will describe here a bit of the 0K quasiharmonic
model. To learn a bit more you can read the extraordinary article of my
late academic son: Miguel Álvarez Blanco:

   [1] MAB et al, Comput Phys Commun 158 (2004) 57

There you will know of a free code (GIBBS) to use this model.
The GIBBS code has a second version, more stable in the mathematical
analysis of data. Unfortunatelly Miguel was not ready at that moment
to publish the GIBBS2 code:

   [2] AOR and VLC, Comput Phys Commun 182 (2011) 1708
   [3] AOR and VLC, Comput Phys Commun 182 (2011) 2232

If you are interested in the big idea read carefully [1]. [2] is
devoted to the mathematical treatment of data, and [3] describes how
to use  wien2k to do this kind of analysis. Unfortunatelly we no longer
have acess to wien2k, so maybe its current output will need a bit of
work from your part ;-)

Regards,
        Dr. Víctor Luaña
--
     .  .     "La suma de la mediocridad y de la creatividad es
    / `' \   constante: a más de la una menos de la otra"
   /(o)(o)\             (Jorge Wasenberg, 2015)
  /`. \/ .'\          "mediocrity+creativity=constant"
 /   '`'`   \ (First Principle of thermodynamics,Universal version)
 |  \'`'`/  | "Lo mediocre es peor que lo bueno, pero también es peor
 |  |'`'`|  | que lo malo, porque la mediocridad no es un grado, es una
  \/`'`'`'\/  actitud"
===(((==)))==================================+=========================
!            Dr.Víctor Luaña                 ! Mediocre is worse than
! Departamento de Química Física y Analítica ! good, but it is also
! Universidad de Oviedo, 33006-Oviedo, Spain ! worse than bad, because
! e-mail:   victor at fluor.quimica.uniovi.es   ! mediocrity is not a grade,
! phone: +34-985-103491  fax: +34-985-103125 ! it is an attitude
+--------------------------------------------+
 GroupPage : http://azufre.quimica.uniovi.es/  (being reworked)