[Wannier] Cu2ZnSnSe and Cu2ZnSnS (Boltzwann Calculations)

[Giovanni Pizzi]

Dear Alex
if the band structure is the same, the results should be comparable.

There are two possible sources of difference that come to my mind:
1. The Wannier-interpolated band structure is different (e.g. because 
the Wannierization is not converged). Did you check if WFs are real, and 
the interpolated band structure is the same as the one calculated with VASP?

2. The interpolation procedure is different in the two codes. Did you 
check in both codes that the results do not depend on the density of 
k-points used for the interpolation/integration?

Also, the value that you state is evaluated at which chemical potential 
and temperature?

Giovanni


On 10/17/2016 03:27 PM, Alex Gal Aziz wrote:
>
> Thanks for the message,
>
>
> I have done a check with one calculation with BoltzTRAP and Boltzwann 
> using PBE+U. Although the trend seems to be the same, the values are 
> not really the same. The BoltzTRAP calculation gives values about 
> 100μV/K higher. Around 500μV/K for BoltzTRAP compared to 400μV/K for 
> Boltzwann.
>
>
> I believe the error must be on my part, but changing the number of WF 
> doesn't change the result. I have kept the Bandstructure frozen till 
> about 1 eV above the lowest conduction band.
>
>
> Any ideas would be welcome.
>
>
> Thanks
>
>
> Alex Aziz
>
> PhD Student
>
> University of Reading
>
>
>
> ------------------------------------------------------------------------
> *From:* Wannier <wannier-bounces at quantum-espresso.org> on behalf of 
> Nicki Frank Hinsche <nicki.hinsche at physik.uni-halle.de>
> *Sent:* 01 September 2016 21:38
> *To:* wannier at quantum-espresso.org
> *Subject:* [Wannier] Cu2ZnSnSe and Cu2ZnSnS (Boltzwann Calculations)
> Hej Ali,
>
> this depends heavily on the charge carrier concentration. The 
> difference due to bipolar effects will be way more pronounced at high 
> temperatures and/or low charge carrier concentrations. The size of the 
> gap merely plays a role in the degenerate limit.
>
> bests
> Nicki
>
> --------------------------------------------------------
> Nicki Frank Hinsche, Dr. rer. nat.
> HC Ørsted Postdoc
> CAMd, Technical University of Denmark
> Fysikvej, Bld. 307, Room 208
> 2800 Kgs. Lyngby, Denmark
> Tel.: ++45 45 25 31 84
> --------------------------------------------------------
>
> > Message: 1
> > Date: Thu, 1 Sep 2016 10:03:04 +0000
> > From: Alex Gal Aziz <A.G.Aziz at pgr.reading.ac.uk>
> > To: "wannier at quantum-espresso.org" <wannier at quantum-espresso.org>
> > Subject: [Wannier] Cu2ZnSnSe and Cu2ZnSnS (Boltzwann Calculations)
> > Message-ID:
> > 
> <VI1PR0101MB2365665CF6E0025C9742F44AD1E20 at VI1PR0101MB2365.eurprd01.prod.exchangelabs.com>
> >
> > Content-Type: text/plain; charset="iso-8859-1"
> >
> > I am investigating Cu2ZnSnSe4 and Cu2ZnSnS4.
> >
> >
> > I have been using VASP compiled with Wannier functions to generate 
> the initial projections and then generate the MLWF using the 
> Disentanglement procedure. I have checked the band structures and they 
> look correct with the appropriate band gaps (~1.5 for Cu2ZnSnS4 and 
> 0.9 Cu2ZnSnSe4).
> >
> >
> > When I check the Seebeck using BoltzWann I seem to get similar 
> results in both cases. I am trying to figure out if this seems 
> plausible due to the difference in band gaps.
> >
> >
> > Any suggestions would be welcomed
> >
> >
> > Thanks
> >
> > Alex Aziz
> >
> >
> > PhD Student
> >
> > Department of Chemistry, University of Reading
> > Whiteknights, Reading RG6 6AD
>
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-- 
Giovanni Pizzi
EPFL STI IMX THEOS
MED2 1326
Station 9
CH-1015 Lausanne (Switzerland)
Phone: +41 21 69 31124

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