[Pw_forum] dos

[Stefano Baroni]

I am still rather skeptical. If you apply your reasoning to the free  
electron gas, it seems to me that you would obtain rather weird (to  
say the least) results. I may be wong, and finally the choice on how  
to analyze your data is yours. SB

On May 5, 2009, at 9:26 AM, Gabriele Sclauzero wrote:

>
> Stefano Baroni wrote:
>> Jonas: I am afraid that what you want to obtain does not make much
>> sense. The angular character of any molecular (or Bloch) state  
>> depends
>> on the origin of your reference system. What is "s-like" with  
>> respect to
>> one point has an infinite number of angular components with respect  
>> to a
>> different point. Are you sure you want to add "what is s-like in  
>> Iowa"
>> with "what is s-like in Italy" ??? ;-)
>> Stefano
>
> I agree with what you say, Stefano, about taking the expectation  
> value of the angular
> momentum in a periodic system, but summing the PDOS of selected  
> atoms can lead to
> meaningful and sometimes very useful results, in some cases.
> I usually see the PDOS as an indicator of how much the Bloch states  
> retain a kind of
> "atomic character" in the solid (so that in this case summing PDOS  
> of equivalent atoms is
> the more meaningful thing, as Lex pointed out), but also as a way to  
> identify the symmetry
> of states.
> If you place a molecule, a nanowire or maybe even a surface with  
> slab geometry in a wise
> manner in your (super-)cell you can get many information from the  
> PDOS (summed or not).
> Obviously, it does not make much sense to sum the s,p,d PDOS of all  
> atoms in the system in
> general (but in some cases it may), so that's why you cannot find it  
> directly in the
> output from projwfc.
> It's your task to select over which atoms you can do a sum (or an  
> average) of the PDOS
> (and also placing the atoms in a smart way, first). I think you can  
> write a script in
> awk/perl/whatever, or even a small fortran program, which reads PDOS  
> from individual files
> associated to the selected atoms and sums the corresponding rows.
>
> Gabriele
>
>>
>> On May 4, 2009, at 5:51 PM, Jonas Baltrusaitis wrote:
>>
>>>
>>> I just successfully calculated DOS and PDOS of a very large system.
>>> One thing that confuses me is the presence of s, p components to  
>>> PDOS
>>> for every atom, but not summed (or averaged) s and p contribution of
>>> all system. I would be happy to find in my output total DOS, PDOS s
>>> character and PDOS p character. Is there a way to get that instead  
>>> of
>>> contribution per every atom? Or how do I proceed to get s and p PDOS
>>> for all system by manually processing all of my 76 atoms PDOS  
>>> outputs?..
>>>
>>> thanks
>>>
>>> Jonas Baltrusaitis
>>> University of Iowa
>>>

---
Stefano Baroni - SISSA  &  DEMOCRITOS National Simulation Center -  
Trieste
http://stefano.baroni.me [+39] 040 3787 406 (tel) -528 (fax) /  
stefanobaroni (skype)

La morale est une logique de l'action comme la logique est une morale  
de la pensée - Jean Piaget

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