[Wien] New exchange-correlation potential

[yhzhao]

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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