[Pw_forum] dos

[Cyrille Barreteau]

Dear Stefano,

Of course if you take the extreme case of the free electron gas, the 
local PDOS is obviously not more relevant
than asking what it is s-like in Italy:-) (but maybe we could discover 
some interesting pertubation around Berlusconi brain:-)
But in many cases  the local PDOS can be very useful to analyze DFT results:
   -local magnetism
  -surface reactivity
not to mention transport properties (STM images etc....)

cyrille

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Stefano Baroni wrote:

> 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)
>
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> de la pensée - Jean Piaget
>
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