[Wien] mBJ + SOC :: spin-orbit splitting reduction

[Martin Gmitra]

Dear Peter,

Thanks for your answer. Could you please give me a starting hint how
to couple mBJ with PBE correlation instead LDA (I do not see any
"flag", needed code modification)?

Best regards,
Martin Gmitra
Uni Regensburg

On 2/6/15, Peter Blaha <pblaha at theochem.tuwien.ac.at> wrote:
> Hi,
>
> Sorry, I have no idea what the SO splitting of those previous
> calculations has been.
>
> In order to get an estimate, compare the partial charges of those
> splitted states. If there is a slight change in hybridization with
> slightly modified s,p,d character of the two atoms, it may explain the
> modified SO splitting.
>
> I'm also not sure at all if the character of the bands using mBJ is
> better than in PBE, in fact I doubt it a little bit.
>
> Eventually you could play with correlation, i.e. couple mBJ exchange
> with PBE correlation instead of LDA.
>
> Am 05.02.2015 um 21:46 schrieb Martin Gmitra:
>> Dear Wien2k developers,
>>
>> We are observing underestimating trend of spin-orbit coupling
>> splittings of Gamma_{15} bands in zinc-blende semiconductors.
>>
>> For instance in GaAs, the Gamma_{15v} splits to Gamma_{8v} and
>> Gamma_{7v} by the values of about 0.29 eV, while experiment gives 0.34
>> eV. PBE calculations gives 0.32 eV. Similar one sees for Gamma_{15c}
>> which splits due to spin-orbit to Gamma_{8c} and Gamma_{7c} where mBJ
>> gives 0.156 eV and PBE 0.181 eV. This one can compare to 0.174 eV from
>> GW+SOC calculations [PRL 96, 086405].
>>
>> In PRB 82, 205212 you present two implementations of mBJ, within
>> Wien2k and VASP. Could you please provide information whether both the
>> implementations provide the same spin-orbit splittings of Gamma_{15}
>> states?
>>
>> In case they are the same, which part of the Becke-Johnson approach
>> can be responsible for such a reduction?
>>
>> Best regards,
>> Martin Gmitra
>> Uni Regensburg
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>
> --
> Peter Blaha
> Inst.Materials Chemistry
> TU Vienna
> Getreidemarkt 9
> A-1060 Vienna
> Austria
> +43-1-5880115671
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-- 
Martin Gmitra
Institute for Theoretical Physics
University Regensburg
93040 Regensburg
Germany