[Wien] New exchange-correlation potential

[F. Tran]

You are using -p to do a parallel calculation and another user has just
reported a bug for parallel calculations with MBJ (see the previous
email of P. Blaha in the WIEN2k mailing list). Try also without -p.


On Thu, 10 Jun 2010, yhzhao wrote:

> Hello,
> 
> I have got a band gap of 0.8 eV, with lattice constant 5.6533 Angstrom and the
> space group No. is 216, with two atoms in (0.0 0.0 0.0) and (0.25 0.25 0.25).
> 
> I have checked that:
> 
> 1. In GaAs.inm_vresp, YES has been replaced by NO;
> 2. I have done the calculation as following steps:
>     For the first scf run, I have set NR2V and indxc=5 in GaAs.in0;
>     Change NR2V to R2V and run one more scf cycle;
>     save lda;
>     Set indxc=28 in GaAs.in0;
>     cp GaAs.in0 GaAs.in0_grr and set index=50 in GaAs.in0_grr
>     run_lapw -p -cc 0.00001
>     plot bandstructure
> 
> Anything wrong with my procedure?
> 
> yonghong
> On 2010年06月10日 05:06, F. Tran wrote:
> > Which value do you obtain? Did you use the correct structure?
> > In Table 1 of the following paper:
> > Tran et al., J. Phys.: Condens. Matter 19, 196208 (2007)
> > it is indicated which structure and lattice constant were used.
> >
> > In case.inm_vresp, you have to replace YES by NO for the normalization.
> >
> >
> > On Wed, 9 Jun 2010, yhzhao wrote:
> >
> >    
> > > Hi,
> > > I have do all your suggested things, which given in the usersguide.
> > > However I
> > > cannot get the band gap, that is 1.64 eV for GaAs, as suggested by PRL
> > > 102,
> > > 226401 (2009).
> > >
> > >
> > > yonghong
> > > On 2010年06月09日 17:54, F. Tran wrote:
> > >      
> > > > 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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> > > > >
> > > > >
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> 
>