[Pw_forum] too many states in PDOS

Guido Fratesi fratesi at mater.unimib.it
Thu Feb 26 12:13:33 CET 2015

Dear Winfred,

there is nothing wrong in what you are plotting. Indeed, with many atoms 
and many electrons the density of states increases and, in other words, 
"states do pack together".

Eventually, in general you want to smoothen out your result so to 
recover something which is closer to the physically relevant limit of 
(supposing you are modeling a bulk system) infinitely large system, for 
which the contribution of individual states would generally be hidden in 
the system's continuum (think to exceptions like states in gaps). Or you 
want to take the DOS with a finite resolution. In both cases one smears 
out the results by attributing to each state a given width (degauss).

Also check that the number of energy points in your plot is consistent 
with the width: i.e., you should have a spacing between the points which 
is smaller than the width of the peaks.


On 26/02/2015 11:11, Winfred Mulwa wrote:
> Dear all,
> I am doing a pdos calculation of a supercell of 72 atoms and
> my nbnd=220 during the nscf calculation. when i draw the graphs
>   using xmgrace, the states looks packed together. Please assist
>    where did i go wrong? attached are the graphs for PDOS and
> spin polarization.
> Regards
> Mulwa Winfred.
> D Phil Student, Computational Material Science Group,
> University of the Free State - QwaQwa,
> South Africa.

Guido Fratesi

Dipartimento di Fisica
Universita` degli Studi di Milano
Via Celoria 16, 20133 Milano, Italy

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