The ABINIT Users Mailing List ( CLOSED )

["Andrew M. Rappe" <rappe@sas.upenn.edu>]

Dear Chol-Jun,

In the particular cases you mentioned, such as Rh,
the issue is the near-degeneracy of the s and d orbitals,
and the importance of achieving norm conservation
for a range of electronic configurations.

These pseudopotentials were designed with care to
reproduce s-d energy splittings and "Tail norms".
In fact we wrote a paper about the importance of this:
I. Grinberg, N. J. Ramer, and A. M. Rappe, 
"Quantitative criteria for transferable pseudopotentials
in density functional theory",
PRB 63, 201102(R) (2001).

I think that all computational methods have some sources of error.  So
to get closer agreement between psp and LAPW would require an
exhaustive analysis of every source of error in both particular codes.

Andrew



On Tue, Feb 05, 2008 at 05:26:12PM +0100 or thereabouts, Anglade 
Pierre-Matthieu wrote:
> Hi,
> 
> Likely, the best would be to ask on the opium mailing list.
> The usual way to improve pseudopotentials is to play with all parameters in
> order to improve the reproduction of the full electron calculation they are
> based on. So the most obvious thing you can try is to
> 1) improve your opium test configurations set to cover more exotic
> situations (this may avoid you trying in Abinit some wrong
> pseudopotentials);
> 2) change the valance of the ionic configuration used to generate the
> pseudopotential;
> 3) create stiffer pseudopotentials;
> 4) play with all other parameters as described in opium tutorials.
> 
> regards
> 
> PMA
> 
> On Feb 5, 2008 4:51 PM, Chol-Jun Yu <yucj@ghi.rwth-aachen.de> wrote:
> 
> > Dear Marc Torent,
> >
> > thank you for your reply. Due to some other reasons, I want to and have
> > to use norm-conserving PP (using Opium package, optimized RRKJ type)
> > rather than PAW. I want to know how to control the parameters in Opium
> > code so as to produce the lattice constant and bulk modulus close to
> > FP-LAPW.
> >
> > Best regards,
> > Chol-Jun
> >
> > TORRENT Marc wrote:
> > > Dear Chol-Jun,
> > >
> > > You could try with PAW "pseudopotentials" (you can find Rd and Pd in
> > > Abinit PAW tables).
> > > PAW always gives results to be compared with (FP)LAPW...
> > >
> > > Marc Torrent
> > >
> > >
> > >
> > > Chol-Jun Yu a ?crit :
> > >
> > >> Dear users,
> > >>
> > >> I would like to ask about the pseudopotential parameter file of Rh and
> > >> Pd. Using the Rh3 and Pd1 GGA
> > >> potential,(http://lorax.chem.upenn.edu/Research/psp_gga.html#Rh3) I
> > >> obtained the results close to experimental values with respect to the
> > >> lattice constant and bulk modulus of their fcc crystals with ABINIT
> > >> code (Ecut=30ha, kpoints=(10,10,10), ixc=11:PBE GGA). However, the
> > >> results are deviated from the LAPW values (Wien2k);
> > >>
> > >>         lattice constant (A)  |  Bulk modulus (Gpa)
> > >>  ----------------------------------------------------
> > >>     |  Exp.    LAPW    PP-PW  |  Exp.  LAPW  PP-PW
> > >>     -------------------------------------------------
> > >> Rh3 |  3.803   3.832   3.806  |  270   260   262
> > >> Pd1 |  3.891   3.940   3.880  |  180   174   186
> > >>
> > >> Is it possible to make the results of PP-PW close to LAPW rather than
> > >> experimental values? If possible, could you provide the generating
> > >> parameter file.
> > >>
> > >> Thanks a lot in advance.
> > >> Chol-Jun
> >
> > --
> > Chol-Jun Yu
> > Computational Materials Engineering (CME)
> > Center for Computational Engineering Science (CCES)
> > Institute of Mineral Engineering (GHI)
> > RWTH Aachen University
> > Mauerstr. 5, D52064 Aachen
> >
> > email: yucj@ghi.rwth-aachen.de
> > phone: 49-0241-80-94989
> >
> 
> 
> 
> -- 
> Pierre-Matthieu Anglade