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Topics - sukhito teh

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1
General Questions and Answers / Papers related to DFT-PPS method
« on: December 18, 2023, 13:56 »
Dear developers and users,

Do you know any paper that explain how DFT-PPS method works or use the method to correct electronic bandgap? I tried but unable to find any related paper.  Or is there a general guide on how to optimize the parameters?

Thank you for your time.

Best regards,
Sukhito

2
Dear developers and users,
I am reaching out to seek assistance in reproducing the results presented in a paper titled "Theory of atomic-scale dielectric permittivity at insulator interfaces" https://journals.aps.org/prb/abstract/10.1103/PhysRevB.71.144104.

I am particularly interested in the calculation of the local dielectric constant. For ionic part, the class 'BornEffectiveCharge' can return values for individual atoms, render the calculation of local dielectric constant feasible. However I can't specify which orbitals to be included in OpticalSpectrum class for calculation of electronic dielectric constant, so I wonder if I can use the derivative functions from Class 'BlochState' to calculate the momentum of individual orbital and thus the local dielectric constant. Could you please provide guidance on whether this approach is viable? Additionally, if there exists a more efficient method for performing the calculations, I would greatly appreciate your insights.

Thank you for your time.

Best regards,
Sukhito Teh

3
Future Releases / Dielectric Constant with Local Field Effect
« on: December 8, 2023, 05:31 »
Dear developers,
From what I understand, the dielectric constant obtained from OpticalSpectrum currently does not account for local field effects, rendering it unsuitable for calculating the dielectric properties of 2D materials. I have observed that QATK now offers GW calculations, and I am curious whether the dielectric tensor involved in GW calculation takes local field effects into consideration. If so, is it possible to save these values for further use?

Thank you for your attention to this matter.

Best Regards,
Sukhito Teh

4
Dear developers and users,
I am working on optimization of slab system 100 atoms ~ 500 atoms. The SCF convergence is working fine, but the geometry optimization took long time to converge. The total energy of the system did go down slowly with optimization steps, but the force remain in the order of ~ 1eV/A after 100 optimization steps. Is there a general guide to improve the convergence speed of geometry optimization.  Thank you for your attention

Best regards,
Sukhito Teh

5
Dear developers and users,
I am trying to calculate work function of TiN using green function method, however the calculation failed to converge nicely at 111 surface, i.e. energy is converged but dQ at central region is still large (~0.15).  The work function obtained seems reasonable, but for other surface calculation, I often obtained dQ that is smaller than 0.01, so I am not sure if I should concern with such value of dQ.

I had also tried different approaches including increases contour points, higher mesh, reducing number of history steps, increase electrode length, central length , but the dQ remained large.

Thank you for your attention

6
Dear developers and users,
May I know if there is a way to change the fermi level in calculation of optical conductivity? From what I understand, anomalous hall conductivity (AHC) can be calculated from optical conductivity at E=0. But with the default fermi energy, I can only calculate AHC at the fermi level. Thanks you for your time.

best regards,
Sukhito

7
Dear Staffs and Users,
I noticed that both GGA+U and HSE06 failed to open the bandgap of FeO. FYI, calculations with VASP can have similar issue, but those can usually be solved by turning off the K-Points symmetry. However,  even if I am setting use_symmetries  = False in AlgorithmParameters, the calculation still assume time reversal symmetry, so I am not sure if similar approach would solve the problem. May I know if there is any suggestion to solve this problem?
Thank you for your time.

best regards,
Sukhito

8
Dear users and developers,
Is there a way to extract local g or local exchange fraction when implementing local dielectric dependent hybrid in DDHCustomExchangeCorrelation? It would be useful for analysis or fitting ddh paramters.

I also tried to calculate the alpha based on the average g using the attached script, however the value always  differ ( usually about 10%) from the value given by ...exchangeCorrelation().exactExchangeFraction(). Other than that, I also wonder if there's a faster way to obtain derivative of electron density other than using the iteration method as stated in the attached script.
Thank you and have a nice day.

9
Dear ATK staffs and users,
I am trying to implement self-defined CLAY force field in molecular dynamic simulation (ATK2022), but keep getting the error "Particle leaving simulation territory!". If I replace the Si and O force field with Pedone_2006Fe2, then the simulation can run smoothly without problem. A similar problem had been posted earlier (https://forum.quantumatk.com/index.php?topic=6641.msg27814#msg27814), does the errors occur because bond potential is not suitable for molecular dynamic simulation?

10
Good day to staffs and users,
I noticed some of the prebuilt classical force fields have incorrect particle mass stated. One of the example is StillingerWeber_MoS_2013(), I wonder why the atomic mass of Mo and S are stated as 1.0 a.u.? Nevertheless, the results based on this potential still give accurate results, hopefully someone can explain to me.
Thank you.

11
Dear developers and users,
Happy new year to all!
I am doing some calculation with the MomentTensorPotentialTraining module and couldn't find a way to extract the fitted parameters. The reason why I am interested in these fitted parameters is to calculate the local potential/forces as mentioned in this paper (https://doi.org/10.1103/PhysRevB.105.115202). Can someone clarify if the extraction is possible within quantumatk?

best regards
sukhito teh


12
Dear developers and users,
I tried to calculate Heisenberg exchange of NiO, and the results show Ni1 and Ni2 have ferromagnetic coupling of about 15.4 meV, which is contradict to experiment or dft results.
I have attached my input files, any comments and suggestions are very much appreciated.

13
Dear developers and users,
I tried to calculate the blochstate of a Bulkconfiguration with spin orbit coupling exchange correlation, yet the result of bloch state is represented in spin up and spin down values. Though I am able to return a result by projecting to Spin.Z axis, when I tried to perform projection to Spin.Y or Spin.X axis, the following error occurs:
Quote
Traceback (most recent call last):
  File "test.py", line 7, in <module>
    arrayx=bloch_state.spinProjection(spin=Spin.X).toArray()
  File "zipdir/NL/Analysis/GridValues.py", line 1145, in spinProjection
NL.ComputerScienceUtilities.Exceptions.NLValueError: Spin not supported: Spin.X
I had attached the input of calculation.

Thank you for your attention.

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