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[Pio Baettig <baettigp@gmx.net>]

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

Attachment: Compare_DOS.pdf
Description: Adobe PDF document

# Elemental Bi test, R-3m
# Convergence with respect to the number of k points and e_cut.

#datasets
ndtset 1

#Definition of the k-point grids
kptopt 1          # Option for the automatic generation of k points, taking
                  # into account the symmetry
ngkpt 6 6 6
nband 40

#Definition of the planewave basis set
ecut 55.0         # kinetic energy cut-off, in Hartree

pawecutdg 60

getwfk 0         # don't restart from previous wavefunctions
prtwf  0         # don't print wavefunctions
prtden 0         #don't print density

#Definition of the unit cell
acell 4.7236 4.7236 4.7236 angstrom
angdeg 57.3476 57.3476 57.3476

#Definition of the atom types
ntypat 1
znucl 83

#Definition of the atoms
natom 2          # two atoms in the rhombohedral unit cell
typat 1 1
xred
0.23407 0.23407 0.23407
0.76593 0.76593 0.76593

#Definition of the SCF procedure
nstep 100          # Maximal number of SCF cycles
toldfe 1.0d-8     # Convergence Criterion (Hartree)
occopt 7          # metallic
tsmear 5.0d-3     #gaussian smearing


#DOS
prtdos 2 #smearing=1, tetrahedron=2
dosdeltae 0.001

#magnetism
nsppol 1