[Wien] problem with DOS calculations

[Md. Fhokrul Islam]

Dear Dr Blaha and Dr Cottenier,

     Thanks for your suggestions. I think I have enough information to get the
job done.


Fhokrul


> Date: Thu, 25 Feb 2010 17:44:14 +0100
> From: pblaha at theochem.tuwien.ac.at
> To: wien at zeus.theochem.tuwien.ac.at
> Subject: Re: [Wien] problem with DOS calculations
> 
> 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
> > _______________________________________________
> > Wien mailing list
> > Wien at zeus.theochem.tuwien.ac.at
> > http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien
> 
> -- 
> -----------------------------------------
> 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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