Topics

1

General Questions and Answers / Dynamicalmatrix huge matrix size

« on: June 20, 2021, 08:56 »

   I am trying to calculate Bi2Se3 "dielectric tensor" with ATK2020.9. I have reviewed manuals and webinars precisely and I found that I should apply "Forcefield" calculator to evaluate "dynamicalmatrix", and "LCAO" to calculate other modules like "optical spectrum, Born charge effects and dielectric tensor".
I found that the reason for this setting might be due the huge computational work in "dynamical matrix". So, exerting "forcefield" calculation will reduce the amount of cpu and ram usage for such module. However, selected configuration of Bi2Se3 is not compatible with "forcefield and semiEmprical" calculators.
Instead of that using LCAO for dynamicalmatrix, after few hours, the simulation stops in the first force calculation because of matrix large size. I tried to set basis with low precision; however, the results does not have enough accuracy like what is mentioned in dynamicalmatrix manual documents.

In the following I have attached the log and the python code.
I will appreciate it if you give advice to solve this issue.

Best regards,
Korand

2

General Questions and Answers / BornEffectiveCharge does not support calculators with spin type Noncollinear

« on: June 11, 2021, 10:05 »

Hi dear friends,

I apply noncollinear spin orbit setting to evaluate dielectric tensor of topological insulator material like Bi2Se3. However, at the end of the simulation I encounter with the following note in log file:

NL.ComputerScienceUtilities.Exceptions.NLValueError: BornEffectiveCharge currently does not support calculators with spin type Noncollinear or SpinOrbit.

Similar to the tutorial I use two calculators, where the first one is used as initial spin for second one.

Best regards,
Korand

3

General Questions and Answers / calculating optical properties (permittivity) at very low frequencies (THz)

« on: May 12, 2021, 20:39 »

Hi dear friends

Earlier I have posted a question about the calculating optical properties at low frequencies. DFT does not give a reasonable answer, I found that this is possible by using Drude-lorentz model. In this model (attached figure), "wi" is natural frequency that will obtain from phonon band diagram or Raman. However, I dont know how to calculated  plasma frequencies in the numerator (here "fi*wi")!
I will appreciate it if you help me.

Best regard,
Korand

4

General Questions and Answers / does photocurrent module limited to illumination from sun?

« on: April 15, 2021, 12:36 »

Hi dear friends,
Does photocurrent module just calculate based on sun flux spectrum. I mean both flux and spectrums can be selected in the module. However, the energy spectrum range limits in this function from 0.3 to 4.5 eV make misunderstanding about the application of this module that it may exclusively belongs to photodetector illuminated by sun.

I want to use that to evaluate my IR detector.

Thanks in advance

5

General Questions and Answers / calculation of optical spectrum versus applied external field

« on: October 9, 2020, 20:21 »

Hi there,

I want to calculate optical spectrum (permittivity) of stacks of graphene layers by changing the external field (EF). Like what we know as changing chemical potential by changing applied EF in articles. How it is possible?
In my calculation I use GGA.PBE function and bulk configuration as version 2016.4 supports Optical Spectrum in this configuration.
I have read topic https://forum.quantumatk.com/index.php?topic=4011.msg18304#msg18304 but the first included link doesn't work properly.
I will appreciate it if you answer my question.