[Wien] New exchange-correlation potential

[F. Tran]

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
> 
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