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

[Abderrahmane Reggad]

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
___
Wien mailing list
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

Re: [Wien] vec2old_lapw

[Nacir GUECHI]

Hi Dear All Wien2k users.
really thanks Dr. Martin Kroeker for your reply. now vec2old_lapw works after 
your advice.

with best regards.
 **
Nacir GUECHI
Dr. Physique de la matière solide.Enseignant-Chercheur à l'université du Dr. 
Yahia FARES de Médéa,  Algeria (www.univ-media.dz).Laboratoire d'études des 
surfaces et interfaces des matériaux solides (L.E.S.I.M.S), université Sétif1 
(Algeria)http://laboratoires.univ-setif.dz/L.E.S.I.M.S/ 

Le Vendredi 18 novembre 2016 23h01, Martin Kroeker 
 a écrit :
 

 You will probably find the "vec2old_lapw" executable (or rather, shell script) 
in the same directory
as lapw2 etc. - what is special about it, is that it is one of a handful of 
tools that relies on 
/bin/tcsh to run it, while most use /bin/csh (on "most" linux systems, /bin/csh 
will be just a link to
/bin/tcsh, but it could be that you have the original csh installed rather than 
its successor tcsh)
-- 
Dr. Martin Kroeker            mar...@ruby.chemie.uni-freiburg.de
c/o Prof.Dr. Caroline Roehr
Institut fuer Anorganische und Analytische Chemie der Universitaet Freiburg

___
Wien mailing list
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


   ___
Wien mailing list
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

[Wien] case.inop output issue

[Dr. K. C. Bhamu]

Dear Users,

I am running an orthorhombic case (a, b and c are different)

I used the following case.inop
9 1   number of k-points, first k-point
-5.0 3.0  Emin, Emax for matrix elements, NBvalMAX
3 number of choices (columns in *outmat): 2: hex or tetrag. case
1 Re xx
2 Re yy
3 Re zz
OFF   ON/OFF   writes MME to unit 4

Choices:
1..Re 
2..Re 
3..Re 
4..Re 
5..Re 
6..Re 
7..Im 
8..Im 
9..Im 



But in the output of case.inop (in other also) I am getting only four
columns two for xx and two for yy components (Re and Img).

# Energy [eV] Re_eps_xx Im_eps_xx Re_eps_yy Im_eps_yy

What is wrong here??



Sincerely
Bhamu
___
Wien mailing list
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

Re: [Wien] Hartree-Fock and the Hubbard Model

[tran]

Hi,

DFT+U is a cheap but rather rough approximation of HF.
Beside this, there is also the difference that in DFT+U, the Coulomb
operator is attenuated in order to account for the screening due to
correlation. In HF, no correlation is included.
In hybrids, the screening is included by using only ~25% of HF exchange
(and there is also correlation coming from a LDA/GGA correlation term).

Hybrid, onsite-hybrid and DFT+U are more or less the same,
since all of them are one-electron methods and mix HF with LDA/GGA.
As Karel said, they are better than LDA/GGA, but can not reproduce
the experimental observations that are beyond the one-electron methods.
DMFT is better since it is a beyond one-electrons method.

Read that:
https://en.wikipedia.org/wiki/LDA+U

FT


On Wed, 16 Nov 2016, delamora wrote:


Dear Fabien Tran and Karel Vyborny,

Thanks for your comments.


What I want to know is if the Hartree Fock exchange is what the Hubbard U is
trying to model

What I know is that for strong intraatomic repulsion, 3d and 4f, the Hubbard
U gives good results, although the U is a parameter.

But for intermediate intraatomic repulsion, 4d, 5d, 5f then more expensive
methods are needed, such as DMFT

So, if this is the case that the Hartree Fock exchange is what the Hubbard U
is trying to model then the hybrid functionals would do a better job.

So, my question is; What are the Hubbard U and DMFT trying to model?


Cheers

  Pablo de la Mora___
Wien mailing list
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

Re: [Wien] Hartree-Fock and the Hubbard Model

[Karel Vyborny]

Dear Pablo,
experts in strongly correlated systems may correct me but my understanding 
is that Hubbard U is not a "model" of Hartree Fock exchange. HF is an 
approximative treatment of electron-electron interaction, a many body 
problem. Hubbard model (where U was originally introduced) tries to 
_model_ the same.


In other words, both Hubbard U and DMFT are attempts to capture the effect 
of electron correlations which are beyond HF.


Best regards,

Karel



--- x ---
dr. Karel Vyborny
Fyzikalni ustav AV CR, v.v.i.
Cukrovarnicka 10
Praha 6, CZ-16253
tel: +420220318459


On Wed, 16 Nov 2016, delamora wrote:



Dear Fabien Tran and Karel Vyborny,

Thanks for your comments.


What I want to know is if the Hartree Fock exchange is what the Hubbard U is
trying to model

What I know is that for strong intraatomic repulsion, 3d and 4f, the Hubbard
U gives good results, although the U is a parameter.

But for intermediate intraatomic repulsion, 4d, 5d, 5f then more expensive
methods are needed, such as DMFT

So, if this is the case that the Hartree Fock exchange is what the Hubbard U
is trying to model then the hybrid functionals would do a better job.

So, my question is; What are the Hubbard U and DMFT trying to model?


Cheers

  Pablo de la Mora


De: Wien  en nombre de delamora

Enviado: martes, 25 de octubre de 2016 11:05:08 a. m.
Para: A Mailing list for WIEN2k users
Asunto: Re: [Wien] Hartree-Fock and the Hubbard Model  
Este remitente no superó nuestras comprobaciones de detección de fraude y e
s posible que no sea quien parece ser. Obtenga información acerca de la sup
lantación de identidad.
Comentarios

Dear F Tran,

Thank you for your suggestion.

I found another one

http://www.wien2k.at/events/ws2015/Tran-talk_xc.pdf

It could be interesting, ja, ja (spanish accent)

I have not read them yet


Saludos


  Pablo


De: Wien  en nombre de
t...@theochem.tuwien.ac.at 
Enviado: martes, 25 de octubre de 2016 02:25:25 a. m.
Para: A Mailing list for WIEN2k users
Asunto: Re: [Wien] Hartree-Fock and the Hubbard Model  
Hi,

all these methods are somehow based on the Hartree-Fock method,
which is (partially) free of self-interaction error.
The SIE with LDA/GGA is particularly large for localized d or f
electrons, such that LDA/GGA don't work well with these systems.

The onsite LDA+U and onsite hybrid are by far much cheaper than
the full hybrids.

This is a good paper to read:
http://journals.aps.org/prb/abstract/10.1103/PhysRevB.79.035103

F. Tran

On Tuesday 2016-10-25 02:09, delamora wrote:

>Date: Tue, 25 Oct 2016 02:09:24
>From: delamora 
>Reply-To: A Mailing list for WIEN2k users 
>To: A Mailing list for WIEN2k users 
>Subject: [Wien] Hartree-Fock and the Hubbard Model
>
>
>Dear WIEN2k community,
>
>From what I understand the Hubbard Model is to calculate the electronic
>repulsion inside the orbitals, specially in the 3d and 4f.
>
>Is it an approximation for the Hartree Fock exchange?
>
>If this is the case then it can be better calculated exact-exchange
>functionals (1, 2)
>
>1) 4.5.7 Onsite-exact-exchange and hybrid functionals for correlated
>electrons
>
>2) 4.5.8 Unscreened and screened hybrid functionals
>
>Cheers
>
>  Pablo de la Mora
>
>
>

___
Wien mailing list
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