[Wien] New exchange-correlation potential
Ricardo Faccio
rfaccio at fq.edu.uy
Thu Jun 10 00:02:49 CEST 2010
Dear F. Tran
What about the use of total energy for: Volume cell optimization and/or for
evaluation of a particular magnetic arrangement ? Can it be used for
comparative purposes? or the procedure indicates that we need to optimize
everything first (forces and volume) for a particular "variational"
xc-potentinal (eg. PBE, etc) and then proceed with MBJ by doing a single
point?
Best regards
Ricardo
-------------------------------------------------------------------------
Dr. Ricardo Faccio
Prof. Adjunto de Física
Mail: Cryssmat-Lab., Cátedra de Física, DETEMA
Facultad de Química, Universidad de la República
Av. Gral. Flores 2124, C.C. 1157
C.P. 11800, Montevideo, Uruguay.
E-mail: rfaccio at fq.edu.uy
Phone: 598 2 924 98 59
598 2 929 06 48
Fax: 598 2 9241906
Web: http://cryssmat.fq.edu.uy/ricardo/ricardo.htm
---------------------------------------------------------------------------------
----- Original Message -----
From: "F. Tran" <tran at theochem.tuwien.ac.at>
To: "A Mailing list for WIEN2k users" <wien at zeus.theochem.tuwien.ac.at>
Sent: Wednesday, June 09, 2010 6:54 PM
Subject: Re: [Wien] New exchange-correlation potential
> Hello,
>
> In order to use the modified Becke-Johnson exchange potential
> you have to choose indxc=28 in case.in0 and indxc=50 in case.in0_grr.
>
> A few more things:
>
> In case.in0 you also need to replace NR2V by R2V such that the
> exchange-correlation potential is written in case.r2v, which will
> be used in the next iteration.
>
> You need case.inm_vresp such that case.vrespsum (which contains a
> part of the kinetic-energy density) is created.
>
> There is no adjustable parameters.
>
> The LDA correlation potential is added to the MBJ exchange potential.
>
> The LDA exchange-correlation functional is used for the energy.
>
> The MBJ exchange potential is not the derivative of an energy functional,
> which means that the method is not variational (i.e., the orbitals are
> not the ones which minimize the total energy, which is LDA).
> In particular, it means that you can not use forces to optimize internal
> parameters.
>
>
> On Wed, 9 Jun 2010, yhzhao wrote:
>
>> Dear Prof. Pblaha,
>>
>> I have tried to calculate something using the new exchange potential
>> with indxc=50 as suggested by the usersguide. At first I want to repeat
>> some data given by PRL 102, 226401 (2009), for example, the band gap of
>> GaAs. I can get a band gap of 0.7 eV for GaAs, which is much better than
>> 0.3 eV of lda, but not much better than the value given by you in PRL
>> 102, 226401 (2009). In the calculation, I use the experimental lattice
>> constant. The k-grid have been increased as dense as 20x20x20 and RKmax
>> as large as 9.0.
>>
>> Is there any adjustable parameter for the MBJ calculation? Thanks.
>>
>> Regards,
>>
>> yonghong
>>
>> _______________________________________________
>> Wien mailing list
>> Wien at zeus.theochem.tuwien.ac.at
>> http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien
>>
> _______________________________________________
> Wien mailing list
> Wien at zeus.theochem.tuwien.ac.at
> http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien
More information about the Wien
mailing list