Messages

31

General Questions and Answers / Re: some theory backgroud of photocurrent about the indirect gap semiconductor

« on: February 11, 2019, 09:02 »

Hello,

Inelastic transition can be also considered by means of the special thermal displacement method, which we have used to calculate the photocurrent in a silicon p-n junction, see:
https://journals.aps.org/prapplied/abstract/10.1103/PhysRevApplied.10.014026

Best,
Daniele

32

General Questions and Answers / Re: The newest pp pseudodojo pp can support spin orbital coupling

« on: February 11, 2019, 08:58 »

Hi.

No, only OMX and SG15 support spin-orbit coupling in QuantumATK-2018-SP1-1.

Best regards,
Daniele

33

General Questions and Answers / Re: Some basic questions about photocurrent

« on: February 7, 2019, 10:16 »

Dear Guang-Ping Zhang,

A good place to start would be the reference paper for the photocurrent module :

"Efficient First-Principles Calculation of Phonon-Assisted Photocurrent in Large-Scale Solar-Cell Devices"
PHYSICAL REVIEW APPLIED 10, 014026 (2018)

And the associated tutorial and webinar:
https://docs.quantumwise.com/tutorials/photocurrent/photocurrent.html
https://docs.quantumwise.com/webinars/webinars.html#solar-cell-devices-including-temperature-effects

34

General Questions and Answers / Re: problems in running the newly added "OptimizeDeviceConfiguration" module

« on: January 23, 2019, 08:43 »

Hi,

sounds like a license issue more than a scientific question, so it is better to contact the technical support:

https://support.quantumwise.com/portal/home

Best,
Daniele

35

General Questions and Answers / Re: how delete information from hdf5 files

« on: January 21, 2019, 09:32 »

Hi,

the IV Characteristics study object should read in the unconverged states and recalculate them automatically upon restart. Please check:

1) The manual page: https://docs.quantumwise.com/manual/Types/IVCharacteristics/IVCharacteristics.html

2) The tutorial: https://docs.quantumwise.com/tutorials/ivcharacteristics/ivcharacteristics.html

Best regards,
Daniele

36

General Questions and Answers / Re: How to export the spectral current from InelasticTransmission spectrum

« on: January 21, 2019, 09:26 »

Hi,

the method implemented in the InelasticTransmissionSpectrum tool does not allow for the calculation of the spectral current in the same way as done in the TransmissionSpectrum tool. Probably what you need is to use the inelasticCurrent query function, see https://docs.quantumwise.com/manual/Types/InelasticTransmissionSpectrum/InelasticTransmissionSpectrum.html

If you can attach a snapshot of the plot that you are interested in, then we could be more precise.

Best regards,
Daniele

37

General Questions and Answers / Re: Inconsistency in the current analysis for InelasticTransmissionSpectrum

« on: January 9, 2019, 10:46 »

Dear Weixiang,

It makes good sense to me. The peak in the spectral current lies outside the bias window that you have considered for the inelastic transmission spectrum. When you calculate the current at 0.2 V, the total current is obtained by integrating the spectral current between -0.1 V and 0.1 V.

Daniele

38

General Questions and Answers / Re: Electron occupation

« on: December 18, 2018, 13:17 »

Yes, it is a good choice.

39

General Questions and Answers / Re: Electron occupation

« on: November 27, 2018, 09:20 »

Hi,

one solution could be to use Mulliken population analysis:
https://docs.quantumwise.com/manual/Types/MullikenPopulation/MullikenPopulation.html

Best regards,
Daniele

40

General Questions and Answers / Re: NEB

« on: November 7, 2018, 16:07 »

Hi,

What you are experiencing is due to the fact that you have set the same output file for (i) the trajectory_filename and (ii) the output file of the OptimizeNudgedElasticBand class.

In the case of (i) the output will be a new NEB configuration at each NEB iteration. These will be called "Nudged Elastic Band_X" with X being the number of the NEB iteration. The configuration with the highest X value will correspond to the most converged NEB iteration.

In the case of (ii) the only NEB configurations that will be written to the output will be those of iteration 0 and of the final NEB iteration, which should correspond to the fully converged NEB path. 

I would suggest that you set two separate files for (i) and (ii), as shown below. This will allow you to have a clearer overview of the files that are created during the NEB run.

Best,
Daniele

Code

# -------------------------------------------------------------
# Optimize Geometry
# -------------------------------------------------------------
neb_configuration = OptimizeNudgedElasticBand(
    neb_configuration,
    max_forces=0.02*eV/Ang,
    max_steps=200,
    max_step_length=0.2*Ang,
    trajectory_filename='trajectory_NEB.hdf5',
    optimizer_method=LBFGS(),
    preoptimization=True,
    climbing_image=True,
)
nlsave('NEB.hdf5', neb_configuration)
nlprint(neb_configuration)

41

General Questions and Answers / Re: NEB

« on: November 6, 2018, 08:26 »

Hello,

as shown in this tutorial, there should be only two NEB files, one with the non-optimized and one with the optimized reaction path:
https://docs.quantumwise.com/tutorials/neb_pt/neb_pt.html

Could you please attach also the log file of the calculation?

Best
Daniele 

42

General Questions and Answers / Re: Blue Phosphorene

« on: November 6, 2018, 08:20 »

Hi,

see this: https://quantumwise.com/forum/index.php?topic=3410.msg15573#msg15573

Best,
Daniele

43

General Questions and Answers / Re: Fat Band Analyzer

« on: October 30, 2018, 10:32 »

Hi,

the FatBandstructure analysis object also allows for projections on tags.

Best regards,
Daniele

44

General Questions and Answers / Re: What is the effect of existence of a gate in NEGF device calculation?

« on: September 10, 2018, 09:01 »

Dear Weixiang,

the gating effect that you see is correct, you are basically bending the electron bands on the right-hand side upward. You still see some pinning on the right-hand side because the right electrode is not gated.

If you try to simulate the undoped system, then you will see that that gating leads also to a symmetric electronic structure.

Best regards,
Daniele

45

General Questions and Answers / Re: Calculation using STD method cannot get converged

« on: September 7, 2018, 17:01 »

Hi,

As explained in the reference paper, Phys. Rev. B 96, 161404(R) (2017), the STD method is supposed to work well only for systems that are periodic in the C direction, unlike the one that you are investigating.

Regarding the STD simulations, I would suggest to have a look at the projected local density of states to check if there are narrow resonances in the density of states, which could often result in convergence problems at finite bias voltages.  Also, notice that you cannot use the Huckel method for STD simulations.

I would also suggest that you first try to solve the problem with the non-STD device, which is more likely related to lack of screening in the electrode regions at finite-bias voltages.

Best regards,
Daniele