[Pw_forum] Carrier concentration in Si

Khara, Galvin galvin.khara.12 at ucl.ac.uk
Wed Sep 30 18:31:49 CEST 2015

Hey there,

Sorry about the long delay in my reply, I was exploring a different area of my research. I actually want to calculate the carrier concentration of Si from 300 K all the way up to 25,000 K (and potentially more). I don't understand how I could go about doing this without applying F-D smearing (sorry about my lack of knowledge, I'm still a bit unsure how I'd go about doing this using quantum espresso). How would I go about doing the simpler analytical method? Also, if I was going to go down the DFT route, I was planning on using the HSE functional (as it has the best band gap for silicon), but it still can't be used for nscf calculations at the moment right? Thanks again for you help, it's really appreciated.



From: Lorenzo Paulatto <lorenzo.paulatto at impmc.upmc.fr>
Sent: 15 September 2015 14:12
To: PWSCF Forum
Subject: Re: [Pw_forum] Carrier concentration in Si

deal Galvin,
I think that you can assume that band structure does not depend on
temperature. Furthermore, a realistic temperature corresponds to a Fermi-Dirac
smearing temperature which is very small. I.e. 300K correspond to just 2 mRy.
It would take a huge amount of k-points to converge such a calculation.

It would be better to do the calculation without smearing, with just a few
extra bands, compute a very fine density of states, then compute the
occupations directly in the energy domain.

But in the end, what you're going to get is just the integral the FD
distribution, centered on the Fermi energy, from the LUMO up to infinity,
which you can do analytically and depends only on the band gap.

kind regards

On Tuesday, September 15, 2015 10:57:27 AM Khara, Galvin wrote:
> Hey,
> I was wondering if there was a (relatively) straightforward way of
> calculating the carrier concentration of a system using quantum espresso? I
> want to apply an electronic temperature using fermi-dirac smearing, and
> calculate the carrier concentration for Silicon at various electronic
> temperatures.
> Thanks,
> Galvin

Dr. Lorenzo Paulatto
IdR @ IMPMC -- CNRS & Université Paris 6
+33 (0)1 44 275 084 / skype: paulatz
23-24/4é16 Boîte courrier 115
4 place Jussieu 75252 Paris Cédex 05

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