[Pw_forum] Convergence or band-gap problem in orthorhombic CsPbBr3
prasenjit.jnc at gmail.com
Thu Sep 8 06:14:17 CEST 2016
If you are doing the band structure calculations for the orthorhombic
phase, the band gap is severely underestimated even without SO coupling.
The picture becomes better if you relax the structure and then calculate
the band gap. Also with and without van der waals effect the structure
significantly and hence the electronic structure also. For details you can
take a look at a recent work of our's (see both the main paper where the
effect of phonons are discussed and the SI where there is a comparison with
and without vdw on the electronic strucute). The link is given below:
On 8 September 2016 at 07:41, Christoph Wolf(신소재공학과) <chwolf at postech.ac.kr>
> Dear Frederico!
> The experimental band gap is 2.3-2.4 depending on the method used; my band
> gap is less than 0.5 eV – rather drastic underestimation. For the
> orthorhombic phase there are two or three references, but they do not agree
> well in terms of the location of the gap (sometimes gamma, sometimes
> R-point) and I am not sure if they applied scissors (it is not stated in
> the manuscript).
> The interesting thing is that the BSE absorption spectrum for the cubic
> cspbbr3 (a=5.6 A) agrees quite well with my experimental values but the XRD
> pattern suggests I have o-CsPbBr3. I am following the YAMBO GaSb tutorial
> (it calculates exactly what I want to calculate); but I am curios where I
> went wrong with my scf/nscf calculation…
> Thank you for your suggestions!
> Christoph Wolf
> POSTECH university
> Dep. Materials Science and Engineering
> Chung-am ro 77
> Pohang, Gyungbuk
> Republic of Korea
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