[Wien] DOS vs. k-point

[Peter Blaha]

With one k-point you have only "one and the same energy / band". Thus
in a DOS calculation with a tetrahedron-method you get a series of 
"delta-function-peaks", and since you do the DOS for a discrete numerical
energy-grid you will miss most (all) of those delta-functions.

You could write your own little "DOS" program (or even use the "broadening"
program of WIEN2k and take each eigenvalue and broaden it by a small Gaussian.

My recommendation, however, would be to use for the DOS a small "unshifted"
k-mesh (like 4-kpoints,...) (not necessarily for scf, just for the DOS after
the scf cycle). This way you also can "see" and check how big your k-dispersion
really is. 

> Dear all,
>  I plan to plot DOS for a large-unit-cell case.
> Normally one k-point is used for a large unit cell to perform SCF.
> I just read the discussion in the mailing list by Thomas on May 30, 2005.
> It sounds like tetra needs more than one k-point to calculate DOS.
> Is this true? If anyone knows a way to calculate DOS with a single
> k-point, please let know. Or, someone can confirm to me that this
> is not possible.
>  Thank you,
> Chiung-Yuan
> 


                                      P.Blaha
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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/
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