[Wien] Electronic polarization with mBJ

[Peter Blaha]

Difficult to answer, it may even depend on the specific case.

We know that LDA/GGA overestimates "covalency" and does not "localize" 
an ionic compound sufficiently.

mBJ opens band gaps and "localizes the states much more, but as it is 
exchange-only (+LDA correlation) with an emphasis on band-gaps, it may 
overshoot easily.

So I guess it is a nice topic to check whether mBJ would improve or 
overestimate polarization in semiconductors/insulators.

On 06/22/2014 07:28 PM, Oleg Rubel wrote:
> Dear Wien2k Community:
>
> I wonder if mBJ can be useful in calculation of polarization-related
> properties. There are narrow gap semiconductors (like InN), which turn
> into semi-metals with a pure LDA. For polarization calculations we need
> a finite band gap, so LDA+mBJ could be an option.
>
> However, it was mentioned on the list
> (http://www.mail-archive.com/wien%40zeus.theochem.tuwien.ac.at/msg07108.html)
> that mBJ results in a more ionic electron density. I performed a test
> for GaN: LDA polarization is 0.030 C/m2 vs 0.035 C/m2 for LDA+mBJ. So,
> it is indeed more ionic.
>
> Do you think we can trust the polarization value obtained with mBJ?
>
>
> Thank you in advance
> Oleg
>
>
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-- 

                                       P.Blaha
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Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
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