Hi,

0.06 eV from BJ is already very close to experiment and it does
not make sense to try to improve further the agreement.
Furthermore, the band gap is not the only quantity you should
consider for comparison with experiment.

FT

On Sunday 2016-11-20 22:34, Abderrahmane Reggad wrote:

Date: Sun, 20 Nov 2016 22:34:57
From: Abderrahmane Reggad <jazai...@gmail.com>
Reply-To: A Mailing list for WIEN2k users <wien@zeus.theochem.tuwien.ac.at>
To: "wien@zeus.theochem.tuwien.ac.at" <wien@zeus.theochem.tuwien.ac.at>
Subject: [Wien] How to get the experimental gap with mBj,
   PBE+U and EECE methods

Dear Wien Users
I have a material with an experimental gap value of 0.1 ev and when using
different methods I found values far from this value as follows:

* mBJ method:
****************
- The original BJ parametrization : Eg=0.06 ev ---> There is no parameter to
manipulate

- The modified BJ parametrization of P.Blaha and F.Tran: Eg= 1.3 ev --->
Which values for alpha and beta to get the experimental value?

- The others parametrizations give a similar value as for mBJ
parametrization.

* PBE+U (U=3 ev):
*******************

Eg=1.5 ev ----> We can't go under 3 ev for U to maintin the
antiferromagnetic state .

* EECE method:
******************

The two values for alpha (0.25 and 0.1 ) give the same value of gap which
1.5 ev.

How to sove this problem?

NB: The PBE method gives no gap 

Best regards

--
Mr: A.Reggad                                          
Laboratoire de Génie Physique
Université Ibn Khaldoun - Tiaret
Algerie



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