[Pw_forum] what is the different pseudopotential?

Gabriele Sclauzero sclauzer at sissa.it
Thu Apr 9 08:43:41 CEST 2009

Jianping Dai wrote:
> Dear All,
> I am a new user of PWSCF. I want to the difference between the two 
> pseudopotentials:
> *Zn.pbe-van.UPF* 
> <http://www.quantum-espresso.org/pseudo/1.3/UPF/Zn.pbe-van.UPF>   
> (*details* 
> <http://www.quantum-espresso.org/pseudo/upfdetails.php?upf=Zn.pbe-van.UPF>)
> 	 Perdew-Burke-Ernzerhof (PBE) exch-corr
> 	 Vanderbilt ultrasoft
> *Zn.bp-van_ak.UPF* 
> <http://www.quantum-espresso.org/pseudo/1.3/UPF/Zn.bp-van_ak.UPF>   
> (*details* 
> <http://www.quantum-espresso.org/pseudo/upfdetails.php?upf=Zn.bp-van_ak.UPF>) 
> 	 Becke-Perdew gradient-corrected functional
> 	 Vanderbilt ultrasoft
> 		author: ak
> It just generated by differnent author?

No, I think they use different exchange and correlation functional. In order to understand 
which XC functional has been used to build a PP file (before using it), you should look 
inside the file itself (which is plain ASCII text).
In this case you would find these strings:

In Zn.pbe-van.UPF:
  SLA  PW   PBE  PBE    PBE  Exchange-Correlation functional

while in Zn.bp-van_ak.UPF:
  SLA  PZ   B88  P86    BP   Exchange-Correlation functional

The first two codes indicate exchange and correlation functionals for the local spin 
density, while the third and fourth for the gradient corrected part. The fifth is the 
identification code for the whole functional (if existing).
These codes are those reported, for instance, at the beginning of the output of a pw.x 
Each code is mapped to an integer defined inside Modules/functionals.f90. These codes are 
then used to access the corresponding formulas for the exchange and correlations parts, 
which you can find inside flib/functionals.f90 and flib/lsda_functionals.f90 for the 
spin-polarized versions.



> Thanks!
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| Gabriele Sclauzero, PhD Student                  |
| c/o:   SISSA & CNR-INFM Democritos,              |
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