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Re: [abinit-forum] {Spam?} Band Gap from GW approximation!

From: "Matteo Giantomassi" <Matteo.Giantomassi@uclouvain.be>
To: forum@abinit.org
Subject: Re: [abinit-forum] {Spam?} Band Gap from GW approximation!
Date: Sun, 8 Jun 2008 16:07:46 +0200 (CEST)
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Importance: Normal

> Dear Colleagues,
>
> I want to calculate the band gap at Gamma point of ZnS in zincblende
> structure, but
> Abinit stops in "DATASET 3" with message:
>
> check if the k-points for sigma are in the set of BZ
> 0.000000000000000 0.000000000000000 0.000000000000000
> findk : ERROR -
> k-point not in the set of kbz
>
> In the calculation, I set ngkpt= 4 4 4,and
> kpt -1.25000000E-01 -2.50000000E-01 0.00000000E+00
> -1.25000000E-01 5.00000000E-01 0.00000000E+00
> -2.50000000E-01 -3.75000000E-01 0.00000000E+00
> -1.25000000E-01 -3.75000000E-01 1.25000000E-01
> -1.25000000E-01 2.50000000E-01 0.00000000E+00
> -2.50000000E-01 3.75000000E-01 0.00000000E+00
> -3.75000000E-01 5.00000000E-01 0.00000000E+00
> -2.50000000E-01 5.00000000E-01 1.25000000E-01
> -1.25000000E-01 0.00000000E+00 0.00000000E+00
> -3.75000000E-01 0.00000000E+00 0.00000000E+00
> In the tutorial GW, the band gap at " -1.25000000E-01 0.00000000E+00
> 0.00000000E+00
> " is calculated. Now I want to know how to calculate the band gap at
> Gamma(0 0 0), any suggestion will be helpful!
>

Dear Yifeng,

abinit stops because you are asking for GW corrections at a
k-point that is not included in the KSS file.
To calculate the band gap at gamma you have to generate a KSS
file with a k-mesh that includes the origin.

The shift of the mesh is defined by nshiftk and shiftk.
The meaning of these two input variables in explained here:

http://www.abinit.org/Infos_v5.5/input_variables/varbas.html#nshiftk
http://www.abinit.org/Infos_v5.5/input_variables/varbas.html#shiftk

Notice that the default value for nshiftk and shiftk is
1 and 0.5 0.5 0.5, respectively. This means that, by default,
the k-mesh is NOT centered on Gamma.

You might have a look at the input file:

tests/tutorial/Input/tgw1_9.in

to understand how to define an efficient gamma-centered
k-mesh to be used for the KSS generation.

Best Regards,
Matteo Giantomassi

> Thanks in advance,
> Yifeng
>

[abinit-forum] {Spam?} Band Gap from GW approximation!, duan_semi, 06/08/2008
- Re: [abinit-forum] {Spam?} Band Gap from GW approximation!, Matteo Giantomassi, 06/08/2008