[Pw_forum] about density

[Stefano Baroni]

Hi Amin. It is a matter of definition that may or may be not useful,  
according to the use that one makes of it.
The projected density of states reads:

n(\epsilon) = \sum_n | \langle \psi_n | \phi_0 \rangle |^2 \delta 
(\epsilon-\epsilon_n)

where \phi_0 is the orbitals you want to project onto, and \phi_n and  
\espilon_n are eigenpairs of the Kohn-Sham equation. The above  
expression, that can be seen as the imaginary part of the one- 
electron Green's function, is perfectly well defined for any  
localized orbital irrespective of the basis set used to expand the  
Kohn-Sham orbitals. In a nutshell, n(\epsilon) expresses the  
contribution of the localized orbital to the total density of states  
of the system under study.

does this help?

regards - SB



On Oct 8, 2006, at 12:40 PM, Amin Babazadeh wrote:

> dear users
> In espresso code we can calculate the DOS for s,p,or d orbitals  
> but  as i know in pwscf method we expand a plane wave function and  
> use it to find eigenvalues and eigenstete and in the expanded   
> plane wave we don't have a quantum numbers (i mean n & l ) or  
> orbitals.So how we can say that this is a DOS diagram of s orbital  
> or p orbital.
> Sincerely yours
>
> -- 
> AMIN

---
Stefano Baroni - SISSA  &  DEMOCRITOS National Simulation Center -  
Trieste
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