[Pw_forum] polarizability of metals using ph.x
Stefano de Gironcoli
degironc at sissa.it
Mon Oct 1 23:13:32 CEST 2012
Dear Anne Justine,
The frequency dependent polarizability (at imaginary frequency) is a
feature that has been partially implemented some time ago (in adiabatic
LDA/GGA if I remember correctly) in the phonon code and calculates the
response function to a macroscopic electric field at finite imaginary
frequency. It was meant to be used to calculate C6 coefficients of
molecules via the casimir-polder formula.
The problem is that it is coded as extension of the static response
function to an electric field which is only possible for non metallic
systems and requires espil=.true.. so CH4 is ok, Pt is not. even if in
principle at finite imaginary frequency it should be possible to
calculate it even in metals.
That part of the code has not been further developed and probably should
be removed since, as Stefano Baroni was suggesting, it should be
possible to study this property via time dependent DFPT (TDDFPT
subdirectory in QE). I know that there has been some recent work to
extend the algorithm to metals but I don't know if it has been completed
and if it has already percolated in the distributed version.
On 10/01/2012 04:36 PM, anne etindele wrote:
> Dear Stefano Baroni
> Thank you for your massage.
> With ph.x I have been able to calculate frequency dependent polarizabilities
> of some non metallic system. I think that in this calculation, the polarizability is related to the
> displacement of the nuclei (of cause it also implies the displacement of electrons).
> Please find attached to this mail
> * an input for a polarisability calculation of CH4
> * an output of CH4 (the values of polarizability are there)
> * an output of Pt that I get were there is no value of polarizability.Best regards
> Anne Justine ETINDELE
> PhD Student,
> University of Douala ( CAMEROON)
> Descente Mont Essec
> P.O. Box 24157 Douala
> De : Stefano Baroni <baroni at sissa.it>
> À : anne etindele <annetindele at yahoo.fr>; PWSCF Forum <pw_forum at pwscf.org>
> Envoyé le : Dimanche 30 septembre 2012 20h24
> Objet : Re: [Pw_forum] polarizability of metals using ph.x
> Dear Anne,
> I am not sure I understand what you actually expect. The electronic polarizability? (i.e. the dielecric constant such as probed by eels?)
> For that you would need a tddft calculation, which is not implemented in ph.x ...
> On Sep 26, 2012, at 2:45 PM, anne etindele wrote:
> Dear all
>> I am trying to determine the frequency dependent polarisability of metals like
>> Pt and Al using ph.x code. Here is the input I made for the case of Pt:
>> phonons of pt at Gamma
>> 0.0 0.0 0.0
>> In the output file I don't have any value of polarizability. Do I need
>> to modify or to add another parameter?
>> Anne Justine ETINDELE_______________________________________________
>> Pw_forum mailing list
>> Pw_forum at pwscf.org
> 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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