QuantumATK Forum

QuantumATK => General Questions and Answers => Topic started by: nicolapelagalli on March 8, 2019, 16:18

Title: Optical Spectrum - Optical Conductivity
Post by: nicolapelagalli on March 8, 2019, 16:18

Dear QuantumATK staffs,

I'm simulating a semiconductive CNT in order to obtain its optical properties. The optical conductivity has very low values (in my case I'm calculating between 10-1000 GHz), and I think this is due to DFT calculations performed at 0 K. By the way, what should I do to obtain optical conductivity at a temperature greater than 0 K?
By mean mobility calculations is possible to obtain conductivty for different temperatures, but only at steady state if I'm not wrong.

Thanks for your attention.

Title: Re: Optical Spectrum - Optical Conductivity
Post by: Petr Khomyakov on March 11, 2019, 10:58

Please take a look at my post regarding using the Optical Spectrum analysis object for 1D systems, https://forum.quantumatk.com/index.php?topic=6047.msg25673#msg25673.

Title: Re: Optical Spectrum - Optical Conductivity
Post by: nicolapelagalli on March 13, 2019, 19:21

Sorry but I don't understand. That is my previous topic, I can't find any information about my question. I know that quantum ATK computes  simulations on an array of CNTs.

Title: Re: Optical Spectrum - Optical Conductivity
Post by: Petr Khomyakov on March 13, 2019, 21:16

Quote from: nicolapelagalli on March 13, 2019, 19:21

I can't find any information about my question. I know that quantum ATK computes  simulations on an array of CNTs.

Please clarify your question.

Title: Re: Optical Spectrum - Optical Conductivity
Post by: nicolapelagalli on March 18, 2019, 13:08

Sorry again.
How to get optical conductivity for different temperature values?

Title: Re: Optical Spectrum - Optical Conductivity
Post by: Petr Khomyakov on March 18, 2019, 16:04

If you mean the effect of thermal disorder on the optical spectrum and related quantities, you may then use the special thermal displacement method for that, see our docs https://docs.quantumatk.com/manual/Types/SpecialThermalDisplacement/SpecialThermalDisplacement.html and two references therein, as well as the case study https://docs.quantumatk.com/casestudies/std_transport/std_transport.html.

This method was originally developed for optical spectra, and was later generalized to account for elastic electron-phonon scattering in the electron transport calculations. 

Title: Re: Optical Spectrum - Optical Conductivity
Post by: nicolapelagalli on March 28, 2019, 16:00

Thank you, that's what I exactly was looking for.
After calculating Dynamical Matrix (it took almos 4 days  ???), I wrote the script I attched (16,0 CNT STD), and now I get the error shown in the log. I can't get what I'm doing wrong.
It seems something due to dyn_mat dimensions...

Title: Re: Optical Spectrum - Optical Conductivity
Post by: Daniele Stradi on April 1, 2019, 10:23

Hi Nicola,

try to change following statement in the script '(16,0) CNT STD.py':

# Repeat the configuration 3 times in each direction
bulk_configuration = configuration.repeat(1, 1, 3)

to


# Repeat the configuration 3 times in each direction
bulk_configuration = configuration.repeat(1, 1, 1)

the bulk configuration used in the SpecialThermalDisplacement class should be consistent with the that used in the script '(16,0) Carbon Nanotube DynMat.py', not with the number of repetitions used in the dynamical matrix class. 

Best,
Daniele