[Wien] Fwd: Fwd: Band Edge position

[Peter Blaha]

As far as I can see from a short browse, these methods are not "ab initio".

How would you calculate an "absolute electronegativity" from a DFT 
calculation ???
I don't even know what this combined phrase means.

PS: A surface slab calculation shouldn't be too expensive ....


Am 20.12.2019 um 17:58 schrieb Subhasis Panda:
> 
> 
> ---
> 
> Dear Experts,
> 
> I wanted to calculate the absolute band edge energies for RbPbI_3 
> compound only (not any interface like RbPbI3 and TiO2 interface) in the 
> orthorhombic phase. As already suggested, it's a computationally costly 
> work and we don't have enough computational facility also in our 
> institute. I was searching in the internet and got the following 
> information. Looking forward to your expert opinion.
> 
> 
> In the following reference, using Eqn 1(a) & (b) can we estimate that? 
> It requires absolute electronegativity of the semiconductor and the band 
> gap.
> https://doi.org/10.2138/am-2000-0416
> 
> whereas in the following reference, the expressions are a little different.
> http://www.rsc.org/suppdata/cp/c4/c4cp03494e/c4cp03494e1.pdf
> 
> Are these two expressions referring to the same thing?  If not which one 
> shall we use. I've one more query, does absolute electronegativity of a 
> material (semiconductor) changes with its crystal structure type (like 
> bcc, fcc)?
> 
> Looking forward to your reply.
> Thank you and best regards
> Subhasis
> 
> 
> On Fri, Dec 6, 2019 at 12:57 AM Peter Blaha 
> <pblaha at theochem.tuwien.ac.at <mailto:pblaha at theochem.tuwien.ac.at>> wrote:
> 
>     This is not such a simple task. You will have to create a supercell
>     simulating the interface between the two materials.
> 
>     The answer can change depending how you form the interface. Furthermore
>     this can be a complicated task, as the periodicity must fit and one has
>     to test/define various surfaces/interfaces (except if 2 materials
>     happen
>     to grow nicely epitaxically).
> 
>     A simpler but much less accurate approach is to do 2 independent
>     surface
>     slab calculations with sufficient vacuum. From the difference of EF and
>     the coulomb potential in the middle of the vacuum (:VZERO) you get an
>     absolute band edge (actually this is the work function in a solid).
>     However, this method neglects band bending, charge transfer or dipole
>     formations at the interface, which could completely spoil the answer.
> 
>     Am 05.12.2019 um 11:27 schrieb Subhasis Panda:
>      >
>      >
>      > ---------- Forwarded message ---------
>      > From: *Subhasis Panda* <onnyorup.iit at gmail.com
>     <mailto:onnyorup.iit at gmail.com>
>      > <mailto:onnyorup.iit at gmail.com <mailto:onnyorup.iit at gmail.com>>>
>      > Date: Wed, Dec 4, 2019 at 2:31 PM
>      > Subject: Band Edge position
>      > To: A Mailing list for WIEN2k users
>     <wien at zeus.theochem.tuwien.ac.at
>     <mailto:wien at zeus.theochem.tuwien.ac.at>
>      > <mailto:wien at zeus.theochem.tuwien.ac.at
>     <mailto:wien at zeus.theochem.tuwien.ac.at>>>
>      >
>      >
>      >
>      > Dear experts,
>      > How can I estimate the absolute band edge position (CB/VB) of a
>      > semiconductor using Wien2k?
>      > The attached figure is what I'm trying to get.
>      > Looking forward to your kind help.
>      >
>      > --
>      >
>      >
>      >
>      > Best regards,
>      > ------------------------------------------------------------
>      > Subhasis Panda
>      > Assistant Professor
>      > Department of Physics
>      > National Institute of Technology Silchar
>      > Assam, India  - 788010.
>      >
>      > -------------------------------------------------------------
>      >
>      >
>      > --
>      >
>      >
>      >
>      > Best regards,
>      > ------------------------------------------------------------
>      > Subhasis Panda
>      > Assistant Professor
>      > Department of Physics
>      > National Institute of Technology Silchar
>      > Assam, India  - 788010.
>      >
>      > -------------------------------------------------------------
>      >
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>     -- 
>     --------------------------------------------------------------------------
>     Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
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> 
> 
> 
> -- 
> 
> 
> 
> Best regards,
> ------------------------------------------------------------
> Subhasis Panda
> Assistant Professor
> Department of Physics
> National Institute of Technology Silchar
> Assam, India  - 788010.
> 
> -------------------------------------------------------------
> 
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-- 
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Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
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