[Wien] problem of energy gap within mBJ

[halim said]

Dear Prof. Tran,
Hi,

Thank you for your answer, I mean withing GGA, mBJ-GGA, and GGA+U, I found the energy gap around 1 eV.
In principle the experimental gap is about 2 eV.
Where is the problem?
Thank you for your help.
Yours sincerely,
Halim Said
I a 

    Le Vendredi 18 août 2017 23h29, "tran at theochem.tuwien.ac.at" <tran at theochem.tuwien.ac.at> a écrit :
 

 Hi,

What do you mean by 1 eV? Does it mean that all
gaps are at exactly 1.0 eV or in a range like 0.5-1.5 eV?

You can compare your results with those in these two articles:
https://publik.tuwien.ac.at/files/PubDat_197400.pdf
https://publik.tuwien.ac.at/files/PubDat_197196.pdf

Cu2O is a special case for which mBJ and GGA+U are not really
better than GGA.

FT

On Friday 2017-08-18 21:42, halim said wrote:

>Date: Fri, 18 Aug 2017 21:42:24
>From: halim said <halim_said04 at yahoo.fr>
>Reply-To: A Mailing list for WIEN2k users <wien at zeus.theochem.tuwien.ac.at>
>To: "wien at zeus.theochem.tuwien.ac.at" <wien at zeus.theochem.tuwien.ac.at>
>Subject: [Wien] problem of energy gap within mBJ
>
>Dear Professor Peter Blaha, Tran and Wien2k users,
>
>I have computed the energy gap for Cu2O by using GGA, mBJ, and GGA+U, I got same energy gap of 1 eV.
>In principle by using mBJ, the energy gap should be increased close to expermimental value around 2 eV.
>Why mBJ is giving same value as GGA and it is not improved? even I tried GGA+U and the same problem and no thing was changed for all approximations.
>
>I would be thankful for your suggestion and answer to solve the problem.
>
>Sincerely yours,
>
>Halim Said
>
>
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