[Pw_forum] Projected density of states

[Pingo Mutombo]

Hello Gerardo,
Many thanks for the explanation. What I need is to project the 
wavefunctions onto atomic states of particular atoms. In my case, I want 
that "fraction" of the wavefunctions which are localised on adatoms and 
rest atoms. For some reasons , the program" projwfc" stops without 
giving any error message. I thought it was related to the size of the 
unit cell.
Best regards,
                                             Pingo


Gerardo Ballabio wrote:

> On 03/31/05 19:14:40, Pingo Mutombo wrote:
>
>> How can I compute the projected density of states for selected  atoms 
>> of a given supercell? I can calculate the total DOS for a   
>> Si(111)-7x7 surface. However  I am unable to calculate the   
>> projected density of states  probably because of the big size of  the 
>> unit cell(249 atoms). At least I would like to calculate  the  
>> projected density  of states for selected Si atoms (adatom and rest  
>> atoms).
>
>
> Hi Pingo,
> "density of states for selected atoms" isn't a well defined concept  
> in density-functional theory. Indeed, wavefunctions computed by PWscf  
> (or any other DFT code) are "collective" and can't be associated with  
> any particular atom.
>
> You may project the wavefunctions onto atomic states:
>
>   |psi> = (sum over atomic states) <atomic state|psi> |atomic state>
>
> where "atomic state" is s, px, py, pz... for a particular atom; this  
> gives you the "fraction" of wavefunction localized on that atom. Keep  
> in mind however that this is an approximation, because atomic states  
> of different atoms aren't orthogonal in general, thus they don't form  
> an orthonormal set. As a result, the sum of such "fractions" over all  
> atoms may not be exactly 1, and the sum of all "atomic" DOS may not  
> equal the total DOS.
>
> Gerardo
>
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Dr.Pingo Mutombo
Institute of Physics of the Academy of Sciences of the Czech republic
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