[Pw_forum] absorption spectrum &dielectric constant of turboTDDFT

[Manu Hegde]

Hi Dario,
Thanks. My unit cell already big contains 80 atoms, I will try to calculate
using supercell.

Regards,
Manu


On Thu, Jul 21, 2016 at 4:02 PM, dario rocca <roccad at gmail.com> wrote:

> Hi Manu,
> The last release of the code does not allow for k-point sampling, that's
> why you get an error message.
> You would need to use a supercell. If you have done a gamma only
> calculation for your system that's probably why you get a spectrum
> that does not match at all experiments.
> Additionally, the Bethe-Salpeter equation is considered the most accurate
> method for bulk solids.
> Best,
> Dario
>
> On Thu, Jul 21, 2016 at 9:42 AM, Manu Hegde <mhegde at uwaterloo.ca> wrote:
>
>> Hi Dario,
>> Thank you very much. I have done some calculations for UV-Vis (see
>> attached) and it is no where matching my experimental results in case of
>> bcc-In2O3. Is it due to pseudopotential (I have used PBE USPP)?. Also I am
>> unable to BZ sampling on k-mesh and TDDFT shown me an error.
>>
>> Regards,
>> Manu
>> (University of Waterloo)
>>
>> On Wed, Jul 20, 2016 at 8:09 PM, dario rocca <roccad at gmail.com> wrote:
>>
>>> Dear Manu,
>>> You can simply extract it with the command
>>> $ grep "S(E)" prefix.plot_chi.dat  > file_for_plot
>>> and use your favorite program to plot it.
>>> Best,
>>> Dario
>>>
>>> On Wed, Jul 20, 2016 at 10:49 AM, Manu Hegde <mhegde at uwaterloo.ca>
>>> wrote:
>>>
>>>> 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
>>>>>>
>>>>>> _______________________________________________
>>>>>> Pw_forum mailing list
>>>>>> Pw_forum at pwscf.org
>>>>>> http://pwscf.org/mailman/listinfo/pw_forum
>>>>>>
>>>>>
>>>>>
>>>>> _______________________________________________
>>>>> Pw_forum mailing list
>>>>> Pw_forum at pwscf.org
>>>>> http://pwscf.org/mailman/listinfo/pw_forum
>>>>>
>>>>
>>>>
>>>> _______________________________________________
>>>> Pw_forum mailing list
>>>> Pw_forum at pwscf.org
>>>> http://pwscf.org/mailman/listinfo/pw_forum
>>>>
>>>
>>>
>>> _______________________________________________
>>> Pw_forum mailing list
>>> Pw_forum at pwscf.org
>>> http://pwscf.org/mailman/listinfo/pw_forum
>>>
>>
>>
>> _______________________________________________
>> Pw_forum mailing list
>> Pw_forum at pwscf.org
>> http://pwscf.org/mailman/listinfo/pw_forum
>>
>
>
> _______________________________________________
> Pw_forum mailing list
> Pw_forum at pwscf.org
> http://pwscf.org/mailman/listinfo/pw_forum
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.quantum-espresso.org/pipermail/users/attachments/20160721/8144486f/attachment.html>