Re: [Wien] problem of energy gap within mBJ

2017-08-19 Thread Gavin Abo

In [1], it says:

/In Refs. [77,82] we showed that a correct description of the band gap 
and electric-field gradient (EFG) in Cu2O could only be achieved with 
the hybrid functionals, while the resultsobtained with the LDA, GGA, 
LDA+U, and mBJ methodswere qualitatively wrong./


In TABLE IV of [2], GGA (PBE) gap is 0.53 eV.  In TABLE I of [3], mBJ 
gap is 0.82 eV.


I'm not seeing a WIEN2k value reported for GGA+U, but maybe it is close 
to the 0.79 eV gap (AMF, U = 8 eV) LDA+U calculation [2] or the 0.67 eV 
gap (with U of 7 eV) GGA+U calculation by VASP [4].


The 0.53 eV, 0.82 eV, and 0.67 eV above round up to be approximately 1.0 
eV, which is around the 1.0 eV that you report.


On the other hand, GGA+U+mBJ calculation may give 1.60 eV [6].

[1] https://publik.tuwien.ac.at/files/PubDat_238321.pdf

[2] https://publik.tuwien.ac.at/files/PubDat_197400.pdf

[3] https://publik.tuwien.ac.at/files/PubDat_197196.pdf

[4] http://dx.doi.org/10.1063/1.3231869

[5] http://dx.doi.org/10.1063/1.4798706

[6] http://dx.doi.org/10.1063/1.4798706 (TABLE I)

On 8/18/2017 9:14 PM, halim said wrote:

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, "t...@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 >
>Reply-To: A Mailing list for WIEN2k users 
>
>To: "wien@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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Re: [Wien] problem of energy gap within mBJ

2017-08-18 Thread 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, "t...@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 
>Reply-To: A Mailing list for WIEN2k users 
>To: "wien@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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Re: [Wien] problem of energy gap within mBJ

2017-08-18 Thread tran

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 
Reply-To: A Mailing list for WIEN2k users 
To: "wien@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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Wien@zeus.theochem.tuwien.ac.at
http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien
SEARCH the MAILING-LIST at:  
http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html