[WIEN]: Bandgaps calculations

[Pablo de la Mora]

Dear Peter,
    Thank you very much
        Pablo de la Mora

Peter Blaha wrote:

>Of course, the Kohn-Sham eigenvalues are not supposed to be the experimental
>measured excitation energies. Nevertheless, many people use them as such.
>
>Experience (and some theoretical considerations as the "discontinuity problem")
>has shown, that for insulators/semiconductors the gap comes out about 50 % too 
>small (and for very small gap semiconductors it may vanish at all); while
>for metals the bands (in particular around EF) are pretty good (though not
>perfect) in many cases (fermi surfaces, angle resolved photoemission).
>
>Thus I'd expect that for MgB2 the bands agree quite well with PES or FS
>measurements.
>
>I would NOT use the Engel-Vosko GGA (option 25) for metals !
>
>
>  
>
>>Dear WIEN users,
>>   If the gaps are not correct with the three options in the program; then in
>>the case of several bands the bandedges should not be very precise. Is that
>>correct?
>>   For example, in MgB2 there are four bands at Ef, but two of them have the
>>upper edge at ~0.8eV is this value correct?
>>   Is the GGA option 25 stil available and would it give the correct values
>>for these cases?
>>   Yours
>>
>>         Pablo de la Mora
>>-------------------------------------------
>>Peter Blaha wrote:
>>
>>    
>>
>>>====
>>>Peter Blaha <pblaha at theochem.tuwien.ac.at>
>>>submitted the following contribution:
>>>====
>>>
>>> 
>>>      
>>>
>>>>I make calculations of AlN,GaN and InN in wurtzite structure using
>>>>WIEN97.10
>>>>
>>>>The bandgaps for AlN y GaN are 50% below of the experimental value, but
>>>>the bandgap for InN is zero.
>>>>   
>>>>        
>>>>
>>>This is what LDA or the common GGAs give.
>>>
>>> 
>>>      
>>>
>>>>How I can make calculations more precise of bandgaps in WIEN97.10?
>>>>   
>>>>        
>>>>
>>>You can use GGA option 25. This is due to Engel and Vosko. It gives much
>>>better bandgaps (often even pretty good), but you have to pay a price:
>>>Never use the total energy! Equillibrium volumes,... are way too large.
>>>
>>>      
>>>
>>    
>>
>
>
>                                      P.Blaha
>--------------------------------------------------------------------------
>Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
>Phone: +43-1-58801-15671             FAX: +43-1-58801-15698
>Email: blaha at theochem.tuwien.ac.at    WWW: http://info.tuwien.ac.at/theochem/
>--------------------------------------------------------------------------
>_______________________________________________
>Wien mailing list
>Wien at zeus.theochem.tuwien.ac.at
>http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien
>
>  
>

-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://zeus.theochem.tuwien.ac.at/pipermail/wien/attachments/20051116/6c8c2f56/attachment-0001.html