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["matthieu verstraete" <matthieu.jean.verstraete@gmail.com>]

Hello,

for the magnetization in particular, your tsmear is quite high. This will occupy a few of the minority spin bands and lower the total M (a bit).

The GGA overestimation of acell is normal, and possibly worsened by the tsmear... For these systems even more than others the pseudopotential is crucial. I am not surprised the GGA is worse - it can be more delicate to make good potentials. Try another one! Or just use LDA, it's miraculously good as a rule. Did you use the potentials from the full TM tables?

Your toldfe is also a bit too high. 1e-10 is decent, depending on what properties you need.

Matthieu

On Sat, Jan 17, 2009 at 7:31 PM, <ldamewood@gmail.com> wrote:

I've been calculating the gap and magnetization in ZB CrAs using abinit. As a
reference, I've been comparing my calculations to Phys. Rev. B 67, 224420
(2003). When I preform an LDA calculation, I get good agreement with the
lattice parameter and magnetization. For the GGA calculation, I get a much
larger lattice parameter and a non-integer magnetization (an integer
magnetization would be expected for half metallic CrAs). Specifically, acell
should be 10.69 whereas GGA gives me 11.2. magnetization should be exactly 3
while GGA gives 2.95.

I've included an input below. Can anyone tell me if I am doing something
incorrectly? I'm not doing anything vastly different in my GGA calculation than
in my LDA calculation so my guess is that the pseudopotential is not well
suited for this calculation. I'm new at this so any help is appreciated.

-Liam

----------------------------------------------------------
For LDA, I used the FHI pseudopotentials and for GGA, I used PBE from the FHI
code. Here is my input file for a GGA calculation for the acell convergence.

[damewood@**** CrAs_1]$ cat CrAs_1.in
ndtset    15
acell:    10.0 10.0 10.0
acell+    00.1 00.1 00.1
rprim     0.0  0.5  0.5
         0.5  0.0  0.5
         0.5  0.5  0.0
ntypat    2
znucl     24 33
natom     2
typat     1 2
xred      0.00 0.00 0.00
         0.25 0.25 0.25
nsppol    2
spinat    0.00 0.00 6.00
         0.00 0.00 -3.00
nband     12

ecut      30.0

kptopt    1
ngkpt     27 27 27
nshiftk   4
shiftk    0.5 0.5 0.5
         0.5 0.0 0.0
         0.0 0.5 0.0
         0.0 0.0 0.5

occopt    4
nstep     20
toldfe    1.0d-6
tsmear    0.01
prtdos    2

-- 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Dr. Matthieu Verstraete

European Theoretical Spectroscopy Facility (ETSF) 
Dpto. Fisica de Materiales, 
U. del Pais Vasco,            
Centro Joxe Mari Korta, Av. de Tolosa, 72,   Phone: +34-943018393
E-20018 Donostia-San Sebastian, Spain        Fax  : +34-943018390

Mail : matthieu.jean.verstraete@gmail.com
http://www-users.york.ac.uk/~mjv500