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Dear Anne Justine,<br>
<br>
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.<br>
<br>
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.<br>
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.<br>
<br>
best regards,<br>
<br>
stefano <br>
<br>
On 10/01/2012 04:36 PM, anne etindele wrote:<br>
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cite="mid:1349102201.90016.YahooMailNeo@web133001.mail.ir2.yahoo.com"
type="cite">
<pre wrap="">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
Cameroon
________________________________
De : Stefano Baroni <a class="moz-txt-link-rfc2396E" href="mailto:baroni@sissa.it"><baroni@sissa.it></a>
À : anne etindele <a class="moz-txt-link-rfc2396E" href="mailto:annetindele@yahoo.fr"><annetindele@yahoo.fr></a>; PWSCF Forum <a class="moz-txt-link-rfc2396E" href="mailto:pw_forum@pwscf.org"><pw_forum@pwscf.org></a>
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 ...
SB
On Sep 26, 2012, at 2:45 PM, anne etindele wrote:
Dear all
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<pre wrap="">
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
&inputph
tr2_ph=1.0d-15,
trans=.false.,
fpol=.true.,
amass(1)=195.078,
prefix='Pt',
outdir='$TMP_DIR'
fildyn='pt.dynG',
/
0.0 0.0 0.0
FREQUENCIES
4
0.5d0
1.0d0
1.5d0
5.0d0
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_______________________________________________
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<pre wrap="">
---
Stefano Baroni - SISSA & DEMOCRITOS National Simulation Center - Trieste
<a class="moz-txt-link-freetext" href="http://stefano.baroni.me">http://stefano.baroni.me</a> [+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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