[Pw_forum] dos

[Axel Kohlmeyer]

On Fri, 2009-05-08 at 17:22 +0200, Stefano Baroni wrote:
> I think the question was slightly different. It would make sense to
> project the DOS onto any localized orbital, and this irrespective of
> the basis set employed (PW's, Gaussians, you name it ...) and of the
> nature of the system (finite or extended), just in the same way as the
> pdos is defined with respect to an atomic orbital. Projecting the dos
> onto a molecular orbital is not implemenetd in QE, as far as I know. A
> quick-and-dirty way of achieving your goal (which would require some
> work, elas!) is the following:

dear stefano,

i agree with this assessment. i don't see a principal technical 
problem to get some _approximation_ of a molecular pDOS, but one 
would have to be very careful in interpreting the results.
 
particularly the notion of anti-bonding MOs worries me. those tend
to have restricted meaning in pseudopotential DFT calculations to 
begin with. now generating them from an approximation and then doing 
a projection on top of it, would make me worry about it being a 
very complicated way to generate quasi-random numbers.

in any case one has to be well aware of the fact, that the molecular
wavefunction that the DOS are projected on is to a significant degree
arbitrarily chosen and it is based on an assumption of non-interacting
molecules. that being said, i can certainly imagine situations where
this kind of procedure would make sense.

cheers,
   axel. 


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Axel Kohlmeyer   akohlmey at cmm.chem.upenn.edu   http://www.cmm.upenn.edu
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