[Wien] New exchange-correlation potential

[yhzhao]

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 In GaAs.inm_vresp, YES has been replaced by NO;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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