The ABINIT Users Mailing List ( CLOSED )

[Marc Torrent <marc.torrent@cea.fr>]

Hi,

Just to be sure...
Did you perform all calculations with the tetrahedron method (i.e. 
prtdos=2 for Abinit, ismear=-5 for vasp or lbroad=-1/0 for hilapw) ?
Are you sure that the k-points sets are the same for the three codes ? 
(note that Abinit uses by default a shifted grid...see shiftk keyword).


Marc Torrent


Pio Baettig a écrit :
> Dear Professor Torrent,
>
> thank you very much for your help.
> I took your input-file, generated a PAW and started the k-point/E_cut 
> optimization this morning.
> So far, it finished up to 40 Ha, the results are as follows:
>
> Metallic Bi convergence test   pawecutdg 60
>          Ecut [Ha]
> K-mesh         15          20          25          30          
> 35          40
> 2*2*2  -144.75633  -144.75707  -144.75719  -144.75731  -144.75714  
> -144.75660
> 4*4*4  -144.73792  -144.73854  -144.73880  -144.73890  -144.73873  
> -144.73852
> 6*6*6  -144.73709  -144.73778  -144.73789  -144.73811  -144.73807  
> -144.73791
> 8*8*8  -144.73606  -144.73717  -144.73726  -144.73736  -144.73740  
> -144.73737
>
> so far, it seems to be converged to 1mHa.
>
> I also looked at the DOS for a calculation with 6*6*6 kpoints,  
> pawecutdg 60 and
> ecut 55 Ha and compared it to a DOS obtained with HiLAPW (6*6*6 kpoints, 
> Wavefunction E_cut 15 Ha, Potential E_cut 60 Ry) and an old result 
> obtained with
> VASP (ecut 16.5 Ha, 6*6*6 k-points).
> The abinit-DOS has slightly different features than the other two which are
> nearly congruent (cf. attached pdf).
>
> I also tried with a bessel scheme and varying rvloc around 2.0, but the 
> features
> of the DOS for metallic Bi did not change.
>
>
> I started calculations for three structures (of different symmetry) of 
> BiAlO3 (Al and O PAW from N. Holzwarth's site) and will compare the 
> relative energies and DOS of these three structures with all electron 
> results and will report on my findings.
>
> Thank you very much,
>
> Best regards,
>
> Pio Baettig
>
>
> Marc Torrent wrote:
> > OK,
> >
> > 1) I think your energy for the second s- state is too close to the 
> > first one;
> >  you should try E=4 or 5 Ry But that's not your problem !
> >
> > 2) If you look carefully at the log derivatives for l=1 (logderiv.1), 
> > you can
> >  see a little divergence around E=-3Ry... You should not have it ! It 
> > could
> > be the sign of a ghost state (not necessarily, but probably). This is
> > generally due to a "too deep" pseudopotential. This is something known 
> > for
> > high Z materials: the norm-conserving Trouillier-Martins scheme gives 
> > hard pseudopotentials for these materials. A solution is to change the 
> > pseudization scheme for the pseudopotential, in order too make it 
> > softer... *
> >  You can try the "ultrasoft" scheme: the pseudopotential is generated 
> > with
> > the same scheme as for TM but the norm-conserving constraint is 
> > suppressed. *
> > You can try the "bessel" scheme: no norm conserving constraint; a 
> > simple pseudization by a Bessel function; but, in the later case you 
> > have to decease
> >  the matching radius (r_vloc) in order to keep the pseudopotential 
> > "hard" enough. Try rvloc=2.0 bohr in your case... and "play" with this 
> > value to test
> >  its influence on physical results.
> >
> > In any case, you have to test both schemes and select the one which 
> > gives better physical results and/or efficiency (size of plane-waves 
> > basis in Abinit).
> >
> > Ultrasoft: simply add "ultrasoft" on the "3 0." line Bessel: replace 
> > or add "bessel" on the "3 0." line
> >
> > I enclose the input file for ultrasoft scheme.
> >
> > Good luck.
> >
> > I'm interessting by having some "feedback" from you: physical results 
> > of your
> >  PAW dataset, cut-off value for 10-3 or 10-4 mHa on energy , .... If 
> > you PAW dataset is "good" enough, I could put it in Abinit table...
> >
> >
> > Marc Torrent