Re: [Wien] How to get the experimental gap with mBj, PBE+U and EECE methods

2016-11-23 Thread Abderrahmane Reggad
Thank you again Prof Tran  and Prof  Laurence for your notes
and guidenesses.

For the procedure to searching the best method giving the best gap I am
looking for .

Best regards



-- 
Mr: A.Reggad
Laboratoire de Génie Physique
Université Ibn Khaldoun - Tiaret
Algerie
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Re: [Wien] How to get the experimental gap with mBj, PBE+U and EECE methods

2016-11-23 Thread tran

As I already wrote previously, 0.06 and 0.1 eV are very close to
each other such that it makes absolutely no sense to try to improve
further the agreement. Also, as mentioned by L. Marks, you need to
figure out if your procedure of searching for the method giving the
correct band gap is meaningful overall.


On Wednesday 2016-11-23 13:07, Abderrahmane Reggad wrote:


Date: Wed, 23 Nov 2016 13:07:45
From: Abderrahmane Reggad 
Reply-To: A Mailing list for WIEN2k users 
To: "wien@zeus.theochem.tuwien.ac.at" 
Subject: Re: [Wien] How to get the experimental gap with mBj,
   PBE+U and EECE methods

Dear prof Tran
I am sorry for the error of the gap value .

The gap value that i want to reproduce is 0.1 ev .

Thank you for your intersting

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



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Re: [Wien] How to get the experimental gap with mBj, PBE+U and EECE methods

2016-11-23 Thread Abderrahmane Reggad
Thank you Prof Laurence for your precious notes.

In my strudy and at the first step, I am intersting to 2 quantities: energy
gap and the magnetic moment.

I am using 3 methods which are the GGA+U, mBJ and EECE and I want to know
the effect of the exchange energy on these 2 quantities through these 3
methods.

I want also to know which one is suitable for the charge transfer insulator.

I need more guides for my study

Best regards

-- 
Mr: A.Reggad
Laboratoire de Génie Physique
Université Ibn Khaldoun - Tiaret
Algerie
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Re: [Wien] How to get the experimental gap with mBj, PBE+U and EECE methods

2016-11-23 Thread Laurence Marks
I am quite disturbed by some aspects of this thread. Trying to adjust the
U, the C in mBJ or something else in order to get a better "fit" to the
band gap verges on misleading science. If you are using the band-gap as a
calibrant and then intend to look at some other property, e.g. charge
transfer or energies this is reasonable. Adjusting it to fit experiment and
then saying that DFT & experiment agree is not something I would allow any
of my students to do.

Some careful thinking is needed, and the same criteria used in experiments
should be used in DFT. It is valid to adjust a parameter "A" using some
dataset "B" (band-gap, heats of formation etc) in order to then fix "A" and
subsequently calculate some other property "C". If "B" and "C" overlap,
this is not valid and verges on misleading science.

On Wed, Nov 23, 2016 at 5:52 AM, t...@theochem.tuwien.ac.at <
t...@theochem.tuwien.ac.at> wrote:

> I don't understand. In a previous email you mentioned an experimental
> gap of 0.1 eV, and now you want to approach 1 eV. So, what is the
> experimental value?
>
> FT
>
> On Wednesday 2016-11-23 12:40, Abderrahmane Reggad wrote:
>
> >Date: Wed, 23 Nov 2016 12:40:55
> >From: Abderrahmane Reggad 
> >Reply-To: A Mailing list for WIEN2k users  at>
> >To: "wien@zeus.theochem.tuwien.ac.at" 
> >Subject: Re: [Wien] How to get the experimental gap with mBj,
> >PBE+U and EECE methods
> >
> >To Prof Tran
> >Since the unmodified version of Beck-Johnson allows me to get 0.06 ev
> which corresponds to the value of C parameter equal to the unity (01). I
> think that to increase of
> >this value would improve the gap value to 1 ev.
> >
> >The question is: Which value for C parameter shall I use to get this gap
> value?
> >
> >Best regards
> >
> >--
> >Mr: A.Reggad
> >Laboratoire de Génie Physique
> >Université Ibn Khaldoun - Tiaret
> >Algerie
> >
> >
> >
> >




-- 
Professor Laurence Marks
"Research is to see what everybody else has seen, and to think what nobody
else has thought", Albert Szent-Gyorgi
www.numis.northwestern.edu ; Corrosion in 4D: MURI4D.numis.northwestern.edu
Partner of the CFW 100% program for gender equity, www.cfw.org/100-percent
Co-Editor, Acta Cryst A
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Re: [Wien] How to get the experimental gap with mBj, PBE+U and EECE methods

2016-11-23 Thread Abderrahmane Reggad
Dear prof Tran

I am sorry for the error of the gap value .

The gap value that i want to reproduce is 0.1 ev .

Thank you for your intersting

-- 
Mr: A.Reggad
Laboratoire de Génie Physique
Université Ibn Khaldoun - Tiaret
Algerie
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Re: [Wien] How to get the experimental gap with mBj, PBE+U and EECE methods

2016-11-23 Thread tran

I don't understand. In a previous email you mentioned an experimental
gap of 0.1 eV, and now you want to approach 1 eV. So, what is the
experimental value?

FT

On Wednesday 2016-11-23 12:40, Abderrahmane Reggad wrote:


Date: Wed, 23 Nov 2016 12:40:55
From: Abderrahmane Reggad 
Reply-To: A Mailing list for WIEN2k users 
To: "wien@zeus.theochem.tuwien.ac.at" 
Subject: Re: [Wien] How to get the experimental gap with mBj,
   PBE+U and EECE methods

To Prof Tran
Since the unmodified version of Beck-Johnson allows me to get 0.06 ev which 
corresponds to the value of C parameter equal to the unity (01). I think that 
to increase of
this value would improve the gap value to 1 ev.

The question is: Which value for C parameter shall I use to get this gap value?

Best regards

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



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Re: [Wien] How to get the experimental gap with mBj, PBE+U and EECE methods

2016-11-23 Thread Abderrahmane Reggad
To Prof Tran

Since the unmodified version of Beck-Johnson allows me to get 0.06 ev which
corresponds to the value of C parameter equal to the unity (01). I think
that to increase of this value would improve the gap value to 1 ev.

The question is: Which value for C parameter shall I use to get this gap
value?

Best regards

-- 
Mr: A.Reggad
Laboratoire de Génie Physique
Université Ibn Khaldoun - Tiaret
Algerie
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Re: [Wien] How to get the experimental gap with mBj, PBE+U and EECE methods

2016-11-21 Thread Abderrahmane Reggad
Thank you Prof Tran for your answer

You think that this value for gap value is enough . For the other quantity
I am interested which is magnetic moment its value is good and doesn't
change a lot for all the cases.

Best regards

-- 
Mr: A.Reggad
Laboratoire de Génie Physique
Université Ibn Khaldoun - Tiaret
Algerie
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Re: [Wien] How to get the experimental gap with mBj, PBE+U and EECE methods

2016-11-21 Thread tran

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 
Reply-To: A Mailing list for WIEN2k users 
To: "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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