[Pw_forum] absorption spectrum &dielectric constant of turboTDDFT

[Manu Hegde]

Hello Dario,

I have done the similar calculations, it went well, after running
turbo_spectrum.x  Do you have any code to extract S(E) or I have to do it
manually?

Manu
(University of Waterloo)

On Tue, Jul 19, 2016 at 8:24 PM, dario rocca <roccad at gmail.com> wrote:

> Dear SungHwan,
> please refer to
> http://arxiv.org/pdf/1402.0486.pdf
> and
>
> http://urania.sissa.it/xmlui/bitstream/handle/1963/5797/turboTDDFT-CPC.pdf?sequence=1
> for more details.
>
> In the output of the postprocessing chi_1_1 is the xx component of the
> dynamical polarizability, chi_1_2 the xy component, etc.
> Often chi is indicated as \alpha in the papers.
> Specifically you would have
>
> Component      energy of the perturbation      real part of
> chi                          imaginary
>                       (indicated either as E or \omega)
> chi_1_1=          0.000000000000000E+00     0.955769346791472E+01
> 0.000000000000000E+00
> .........
>
> As you correctly say the absorption spectrum is related to the imaginary
> part of the average of chi multiplied by E (the energy E is often
> indicated as \omega).
> This averaged quantity is contained in S(E). Specifically S(E) is the
> strength function defined as
> S(E)=2m/(\pi*e^2*\hbar) * E*Im[chi(E)], where chi has been averaged over
> the 3 spatial directions.
> This definition is convenient because S(E) satisfies the f-sum rule.
> So if you extract S(E) and plot it you will have the absorption spectrum.
> Let me know if it's still not clear
> Best,
> Dario
>
>
>
>
> On Tue, Jul 19, 2016 at 4:01 PM, SungHwan Choi <sunghwanchoi91 at gmail.com>
> wrote:
>
>>     hi, I am a newbie for turboTDDFT. Now, I ran a simple example. It was assume.
>> Now I have prefix.plot_chi.dat  file. then I don't know how to generate
>> absorption spectrum from that file and dielectric constant values. As far
>> as I understood, the absorption spectrum is related to imaginary part of
>> average \chi value. but in the file there are 9 values
>>          chi_1_1
>>          chi_2_1
>>          chi_3_1
>>          chi_1_2
>>          chi_2_2
>>          chi_3_2
>>          chi_1_3
>>          chi_2_3
>>          chi_3_3
>> This is 3*3*3 tensor. how do I get an absorption spectrum and dieletric
>> constant values? by the way S(E) means what?
>>
>> Sincerely
>> Sunghwan Choi
>>
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>
>
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