[WIEN] DOS question

[Fotios Nastos]

On November 5, 2003 11:40 am, Andrei Postnikov wrote:
> On Wed, 5 Nov 2003, Yam Chi Yung wrote:
> | Dear all wien users,
> |
> | I tried to calculate the electronic structure of KI. However, when I
> | integrate the density of states up to the Fermi level, I found that it
> | does not equal to the number of electrons. What was the problem?
>
> ... and in addition to what has already been said,
> if your difference is a nearly integer number, then it might be of course
> due to semcoere states which contribute to the total number of
> electrons, but probably are not included in your DOS window.
>
> (Or if they are included, it's even worse:
> the integration of a nearly zero-width peak is of course very inaccurate).

Which seems somewhat ironic, since the tetrahdron method that is used to do 
the integration in calculating the DOS is a linear scheme (LATM), in that it 
linearizes the band structure to use "analytic" expressions for the integral 
over the tetrahedra of the Brillouin Zone.  For a given k-mesh one expects 
the tetrahedron integration routine to work better for semi-core states since 
they are flatter than conduction/valence bands (that is, semi-core bands are 
better approximated by linear fits).  So, the resulting contribution from the 
semi-core states to the DOS spectra, is in a sense more numerically accurate 
than the contribution from the higher states.

Of course, this does not invalidate or contradict previous comments.  I just 
thought it was a little ironic.