Hi,
I just wish to note that in all the cases I have treated SIESTA produces
band gaps much larger than other
plane-wave codes.
For example SiO2 LDA band gap is about 7eV in SIESTA and 5.5eV in ESPRESSO.
Maybe this is related to the SIESTA method itself, or to a non-trivial
choice of the basis set.
However, it is possible that there's nothing wrong with your Ge
calculation, I would just compare the bands with experimental ones.
cheers,
Roberto
On 02/06/2014 05:23 PM, FEDERICO IORI wrote:
Hi all.
Just a comment: a norm conserving LDA pseudo with plane waves (without any
semicore states, nonlinear core correction) nor spin orbit coupling should
give a semimetal for the Ge.
Which flavour of pseudo are you using for Abinit?
Thanks Federico.
Hi Riccardo
We have same kind of problem/observation. We are using Siesta with LDA
(DZP
basis) and it produces an indirect band gap of 0.70 eV. We have also
tested
with plane waves basis using Abinit (cutoff = 95 Ry) and found 0.58 eV.
Chelikowsky et el. (PRB, 40, 1989) using plane waves report an indirect
band gap of 0.81 eV. Wang et el. (PRB, 24, 1981) using LCGO have reported
a
band gap of 0.52 eV.
Regards,
Rafi Ullah
On Thu, Feb 6, 2014 at 3:43 PM, Riccardo Rurali <[email protected]> wrote:
Dear Siesters,
I am having trouble with Ge in LDA with Siesta.
As is well-known, Ge is a pathological case within DFT-LDA: the gap
shrinks so much that is becomes negative, i.e. Ge is metallic in LDA.
However, I'm having problems in recovering this behavior with Siesta and
I
get gaps of 0.4-0.5eV, depending on fine details of the basis set.
I have tried both optimized and automatic DZP basis sets. Short and
long.
"Vanilla" pseudos or pseudos with extra tuning (e.g. core-corrections).
Nothing. The gap's still there.
Has any of you experience with treating Ge with Siesta ans trying to
recover to "right" (which is wrong in reality...) LDA behavior?
Any help would be greatly appreciated.
Riccardo
--
Riccardo Rurali
Institut de Ciència de Materials de Barcelona (ICMAB)
Consejo Superior de Investigaciones CientÃficas (CSIC)
Campus de Bellaterra
08193 Bellaterra (Barcelona)
Spain
tel.: +34 93 5801853 ext. 347
e-mail: [email protected]
http://www.icmab.es/dmmis/leem/
Man, the dope's that there's still hope
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