[Wien] problem with DOS calculations

[Peter Blaha]

I guess we had these questions before.

The TETRAHEDRON method calculates the DOS band by band.
With one k-point a "band" consists only of ONE energy and thus would give a
delta function.  In other words: even if your eigenvalues are at 0.099999 (band 1) and 0.100001
(band 2), the DOS from tetra at 0.10000 is exactly zero (while the integrated DOS (see Stefaans comment)
will increase by 2 electrons for the energies 0.099 and 0.100.

For one k-point, one needs a "histogramm method", i.e. you should specify an energy mesh (eg. 0.005 Ry),
then take case.energy (or case.qtl) and then simply "count" the eigenvalues in each interval (remember,
the DOS is the number of states/energy intervall). Finally you may smoothen the curve and put some
gauss broadening on it.


Stefaan Cottenier schrieb:
> 
>> Addendum: you can take the intermediate output, put them into a
>> spreadsheet such as Excel and plot the dos yourself with some
>> broadening -- it works but is not so convenient.
> 
> Two comments on this:
> 
> 1) you can specify a broadening in case.int (see Sec. 8.1.3 of the UG)
> 
> 2) there is a very robust integration of the DOS plotted in 
> case.outputt. Even if the energy step is too large to see a spike, it 
> will appear clearly as a sudden jump of the integrated value.
> 
> Stefaan
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-- 
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Peter Blaha
Inst. Materials Chemistry, TU Vienna
Getreidemarkt 9, A-1060 Vienna, Austria
Tel: +43-1-5880115671
Fax: +43-1-5880115698
email: pblaha at theochem.tuwien.ac.at
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