[Pw_forum] line crossing Valance bands (VB) & CB

[Paolo Giannozzi]

On Thursday 06 August 2009 18:31, dev sharma wrote:

>  I have successfully calculated the band structure of my system. It is also
> matching the results. But when I plot my band structure in ps format only
> one line from conduction band and valance band is showing fluctuations.
> Means one line ,in ps output, from conduction band has apparently come down
> to valance band and vice versa. And this fluctuation is  just  at the end
> of graph. (means i have given 41 k points in calculations= 'bands' and in
> only last 3 there is some fluctuations, the whole other graphs is smooth
> otherwsie). 

I am not sure I understand what you mean. One possibility is the following:
when one calculates bands, a few high-lying states may not be the correct 
ones because of the way iterative diagonalization works (it starts from
an initial guess). This is a rather normal behavior. The highest states in a
band calculation should be discarded.

Paolo
-- 
Paolo Giannozzi, Democritos and Udine University