[Pw_forum] Dynamic polarizability of C60

[Eduardo Ariel Menendez Proupin]

Hi Anne, and everybody,

My question about the dynamical polarizability was more for the developers,
because I don not find it clear in the documentation.
Let me focus my question

The electronic dynamical  polarizability is calculated with the
turbo-TDDFPT code. Then, what dynamic polarizability is calculated with
PHONON ? Knowing some of he applications of the PHONON code, I foresee two
logical answers
a) the polarizabilty due to phonon excitations, plus the electronic
polarizabilty in the static limit, i.e., for energy much smaller than the
electronic transition energies.
b) the same, but with the frequency dependent electronic contributions,
calculated with ground state DFT instead of TDDFT.
and the answer is c)  ...........?

I do not believe that the frequencies in the example 33 are in Ry. They are
too high if the units are Ry, and PHONON is esentially a code to calculate
phonons and derived properties. I would bet for THz.

best regards
Eduardo


DearEduardo You wanted to know What exactly this dynamical polarizability
is? In fact, when a system (atomic, molecule,...) is submitted to an
external field, its electrons are reorganised according to the frequence of
that external field. One can then evaluate the aptitude of the system to be
subject to that reorganisation by evaluating the polarizability.
Particularly when the phenomenon is time dependent, one evaluate the
dynamical polarizability.    is it include the electronic , phonon or both
contributions?   For my case, I want to consider C60 as a dielectric sphere
of finite or infinite thickness, I don't know exactly if the phonon
contribution is relevant, but I am mostly evolved in electronic
calculations.  What are the frequency units (THz, eV? ) in the example 33.
 As I see in output of that example 33 (it is also the case for almost all
the other input and output files of espresso-4.3.1), the energies and
frequencies are in Ry Kind regard
-- 


Eduardo Menendez Proupin
Departamento de Química Fisica Aplicada
Facultad de Ciencias
Universidad Autónoma de Madrid
28049 Madrid, Spain
Phone: +34 91 497 6706

On leave from: Departamento de Fisica, Facultad de Ciencias, Universidad de
Chile URL: http://fisica.ciencias.uchile.cl/~emenendez

"*Padece, espera y trabaja para gentes que nunca conocerá y que a su vez
padecerán, esperarán y trabajarán para otros, que tampoco serán felices,
pues el hombre ansía siempre una felicidad situada más allá de la porción
que le es otorgada. Pero la grandeza del hombre está precisamente en querer
mejorar lo que es. En imponerse Tareas. En el Reino de los Cielos no hay
grandeza que conquistar, puesto que allá todo es jerarquía establecida,
incógnita despejada, existir sin término, imposibilidad de sacrificio,
reposo y deleite. Por ello, agobiado de penas y de Tareas, hermoso dentro
de su miseria, capaz de amar en medio de las plagas, el hombre puede hallar
su grandeza, su máxima medida en el Reino de este Mundo*".
Alejo Carpentier, El reino de este mundo, (1949).

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