[Wien] Band Labeling

[Dr. Sharat Chandra]

Dear Prof. Blaha

Thanks a lot.

Sharat

On Tue, 25 May 2004, Peter Blaha wrote:

> One labels them according to the irreducible representations.
> 
> Use "irrep" to calculate those representations (for non-symmorphic SG only).
> 
> > How do we label the bands in the band structure that we have calculated
> > for some compound? I have read up some materials on the subject, but till
> > now I have been able to get some rumor level ideas only. Can some body
> > please point out some good references for the topic, and lay out some
> > algorithm as to how to go about it practically? The band structures that I
> > am talking about are for tetragonal materials the data for which is not
> > available do readily in literature.
> >
> > Questions are:
> >
> > 1. How do we get the block matrix and irreducible representations of the
> >    Hamiltonian matrix?
> 
> We do not use symmetry decomposition of the hamilton matrix. It is of course
> correct that in principle one can do this (and it was done in APW some 30-40
> years ago). Nowadays, with low (no) symmetry it does not pay off anymore.
> 
> > 2. How do we assign to the bands the labels based on the point group
> >    operations for some symmetry point?
> 
> See my comments at the top.y