[Wien] help required

Stefaan Cottenier Stefaan.Cottenier at UGent.be
Wed Mar 28 09:25:41 CEST 2012

> I am Working on a Binary compound . when I check its Band Gap value from
> Analysis 0.526 eV but when I closely monitor the Plot Of Band Gap
> visually there is no Gap between conduction and valence band i,e: it is
> showing zero Band Gap Value.
> What the reason behind this difference ?

Assuming that "from Analysis" refers to the Analysis tool in w2web: it 
greps for the last few occurrences of a given string (e.g. :GAP) in 
case.scf. For some properties, the last occurrences is not necessarily 
in the last iteration. The :GAP keyword is printed only if the gap is 
non-zero. It may happen that in the first few iterations there are 
non-zero gap values (which are meaningless, being not converged), while 
the gap disappears at convergence. In such a situation, Analysis in 
w2web (or grepline) will show you still the last non-zero :GAP value.

_Suggestion to the developpers_: wouldn't it be safer to print the :GAP 
keyword anyway in every iteration, even if it is zero? I understand 
there are arguments why printing :GAP=0.000 is not optimal, as this 
could suggest a case to be metal even when this is not true. But maybe a 
text message instead of a numerical zero value?


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