[Wien] How to get lattice parameter as a function of pressure?

Wangwei Lan Fri, 27 May 2016 08:13:15 -0700

Dear WIEN2K user,

Can you tell me how to extract lattice parameter as a function of pressure?
I didn't find it in case.eosfit as mentioned here
http://www.mail-archive.com/wien%40zeus.theochem.tuwien.ac.at/msg04276.html

After x eosfit, in the case.eosfit, I can only find three colums, which I
think corresponding to volum, energy and pressure. But no lattice constant
information. I can't find any lattice constant information in
case.outputeos either.

I guess eosfit6 probably can do this job, however, I don't know how to use
it. Before doing x eosfit, I did,  parabolfit_lapw,  but it always gives me
errors. (see blow)

I hope you can give me some idea. Thanks in advance.

What I have already done,
1)  do x optimize and create 36 cases.
2)  run optimize.job with "save_lapw -d optimize ${i}" which saves all my
data into directory optimize.
3)  grepline :ENE "optimize/*scf" 1 >> case.analysis
      grepline :VOL "optimize/*scf" 1 >> case.analysis
4) eplot_lapw -t vol   This step gives me the plot Energy vs Vol.
5) x eosfit
6) parabolfit_lapw -t 2 -f optimize -scf 'optimize/*.scf'   : This step
gives error like this

ls: No match.
ls: No match.
optimize.ene and optimize.latparam generated
  ERROR IN OPENING UNIT:          10
        FILENAME:
 ZrPSe.ene

    STATUS: old          FORM:formatted
OPEN FAILED

Reply:

1- from Pr Stefaan Cottenier

Re: [Wien] How to get lattice parameter as a function of pressure?

Stefaan Cottenier Fri, 27 May 2016 08:35:48 -0700






Can you tell me how to extract lattice parameter as a function of pressure?
I didn't find it in case.eosfit as mentioned here
http://www.mail-archive.com/wien%40zeus.theochem.tuwien.ac.at/msg04276.html




It would be trivial to do this for a crystal that is entirely determined by the volume (for instance, bcc iron): you calculate energy for a few volumes, do the Birch-Murnaghan fit by eosfit, look for the volume vs. pressure data in case.eosfitb, and convert the volume to lattice parameter.


It becomes somewhat more complicated when you have internal degrees of freedom (let's still assume a cubic crystal for the time being). Again calculate the total energy for a set of volumes. But for every volume, the internal positions should now be optimized first. Once you have done that, the procedure is the same as before, and you can get the lattice parameters out of the volume.


Now drop the requirement of a cubic crystal. Take an orthorhombic one (with or without internal degrees of freedom). Again you need the total energy for a set of volumes. But for every volume you need optimize internal parameters and the three lattice parameters (with the restriction that the volume is kept constant). From these optimizations, you will know what the relation between volume and the three different lattice parameters is. From the fitted volume-pressure relation, you canget any of the lattice parameters as a function of pressure.





Stefaan

2- from Dr Víctor Luaña




Re: [Wien] How to get lattice parameter as a function of pressure?

Víctor Luaña Cabal Fri, 27 May 2016 08:38:57 -0700


On Fri, May 27, 2016 at 11:12:30AM -0400, Wangwei Lan wrote:
> Dear WIEN2K user,
> 
> Can you tell me how to extract lattice parameter as a function of pressure?
> I didn't find it in case.eosfit as mentioned here
> http://www.mail-archive.com/wien%40zeus.theochem.tuwien.ac.at/msg04276.html
If you have the Energy versus volume data for your crystal you can euse
the gibbs2 free code to do all the analysis. You can learn about the
method in

MA Blanco, E francisco and V. Luaña, Comput. Phys. Commun. 158 (2004) 57--72
<http://dx.doi.org/10.1016/j.comphy.2003.12.001>

an improved version of the code was described in

A. Otero-de-la-Roza and V. Luaña, Comput. Phys. Commun. 182 (2011)
1708--1720; 2232--2248
doi:<10.1016/j.cpc.2011.04.016>
doi:<10.1016/j.cpc.2011.05.009>

The code is maintained and you can get the last version and a detailed
manual from

<https://github.com/aoterodelaroza>

Best regards,
             Víctor Luaña