Recent Posts

11

General Questions and Answers / Builder

« Last post by Lil_David on April 1, 2025, 23:30 »

Hello Everyone,

My stash panel and filter panel are not showing on my "builder." Please, what can I do to restore them? I have tried the restore builder layout and also restarted my quantumatk but the issue is not resolved.

Please, I will really appreciate a response; no one responded to my last question on Crystal Builder.

Thank you

12

General Questions and Answers / Source Exhaustion Effects

« Last post by techenthusiast on April 1, 2025, 07:51 »

Dear Experts,

Good morning, hope you are doing well. I have gone through these articles. Here they have mentioned Source Exhaustion Effects. I am enclosing my device structure so that can be comparable with the provided device structure at the literature. Especially for single channel device.  is it correct , the device structure?

https://sci-hub.st/10.1109/iedm.2009.5424281

https://ece.uwaterloo.ca/~l28wei/publications/2011TED_CNT.pdf

13

General Questions and Answers / Re: Effective bandstructure that goes beyond quantuamatk limitation

« Last post by sukhito teh on March 31, 2025, 09:26 »

1. Yes, memory, and you found the right solution - more threads rather than more MPIs per node reduces memory usage but keep the speed roughly the same, in many cases.
2. There are two guides in the manual around performance/parallelization and memory usage:
https://docs.quantumatk.com/manual/technicalnotes/parallelization/parallelization.html
https://docs.quantumatk.com/manual/technicalnotes/advanced_performance/advanced_performance.html
It's hard to give a single advice that works for all systems, but QuantumATK speeds up very well to high count of cores, and the more memory you need, the more you should rely on threading rather than MPI.
3. To me this is a very natural part of the projection algorithm, not least considering the way QuantumATK uses atomic orbitals as basis. It also provides a logical way to interpret the results. If your larger system is not really an extension of something with a smaller periodicity, the effective band structure may not be the best tool to analyze the results. The band gap for any system can always be inferred from the density of states, and the curvature is the same as the effective mass basically, which can also be computed directly for the supercell system.

Thank you for your reply.
1. You are right, the effective bandstructure that I had obtained is indeed very disordered due to poor symmetry.
2. Thanks, I would look into the effective mass module.

14

General Questions and Answers / Query Regarding Crystal Symmetry and Space Group Identification in QuantumATK

« Last post by UtpalLab123 on March 27, 2025, 20:07 »

Dear Sir/Ma'am,

When I compute the crystal symmetry and space group number for my system (plane 2d system), I see an option in the QuantumATK-R-2020.09-SP1 version called "Crystal Symmetry Info." Under this, there are two parameters:
(a) Position, which defines the tolerance of the fractional coordinates when searching for the space group.
(b) Angle, which defines the tolerance of the angles when searching for the space group.
My question is: What values should I use for these parameters to accurately identify the crystal symmetry and space group number?

15

General Questions and Answers / Re: Can we create MTP with dopant atom included?

« Last post by Lim changmin on March 27, 2025, 15:11 »

Thank you for your response.

I am currently working on training an MTP exclusively for amorphous structures, as there is no corresponding crystalline phase.

I have some questions regarding Step 1 of the standard crystalline training protocol. For training amorphous structures, active learning requires both MTP training and a training set generation function. In this process, MTP training is typically initialized using the random displacement function applied to a crystalline structure.

My question is: Can the crystal random displacement function be used for amorphous structures as well? Or is it strictly applicable to crystalline phases?

I am asking because, in the tutorial (https://docs.quantumatk.com/tutorials/mtp_hfo2/mtp_hfo2.html), the workflow in Step 1 explicitly refers to the "bulk phase." I am a bit confused by the term "crystal" in "crystal training random displacement function" and whether it applies to amorphous systems.

I would appreciate any clarification on this.

16

General Questions and Answers / Re: Dipole moment for periodic system

« Last post by Anders Blom on March 26, 2025, 21:36 »

I think those "dipole moments" are a bit different. For the 2D Janus TMDs, I believe the method is as simple as computing the net charge transfer between the two layers and multiplying with the distance between the layers. Granted, you need a clear definition of the "distance", but I imagine the distance between the metal atoms is a reasonable choice.

DOI:10.1039/C7TC05225A
DOI:10.1016/j.cplett.2021.138495
DOI:10.1016/j.apsusc.2022.155163

17

General Questions and Answers / Re: Anders Blom

« Last post by zwh on March 26, 2025, 11:54 »

Dear Anders Blom,

The HDF5 file I need to share is quite large in size, making it difficult to upload via the forum. Would it be possible for you to provide an email address where I can send the compressed file directly? Your assistance would be greatly appreciated.

Thank you for your support.

18

General Questions and Answers / Re: Dipole moment for periodic system

« Last post by sukhito teh on March 26, 2025, 08:28 »

From what I know, the dipole moment can be approximated using equation 7 in this paper https://journals.aps.org/prb/abstract/10.1103/PhysRevB.68.195408 . Another method  is to build a 3D configuration with "2D polarization configuration" (I don't know how to put in words, but you can check the supplementary information in this paper https://iopscience.iop.org/article/10.1088/1361-648X/ab1d0f )

19

General Questions and Answers / The cell size is required to increase for better convergence while execution?

« Last post by techenthusiast on March 26, 2025, 07:32 »

Dear experts,

Good morning, just to ask, normally: For this kind of structure (Long devices), The cell size is required to increase for better convergence while proper task execution? in conventional cases? if yes, how to do that for existing device structure/geometry. Thank you.
Note: I have enclosed the structure.

20

General Questions and Answers / 2D Perovskite Structure

« Last post by Lil_David on March 25, 2025, 23:42 »

Hello Everyone,
 I am trying to build a 2D Cs₂PbI₂Br₂ inorganic layered Ruddlesden−Popper Mixed Halide Perovskite using the crystal builder because it is not available in the database. I am using the right Wyckoff Position for each element, but I keep getting Cs₄Pb₂I₄Br₄. What am I getting wrong?

I tried replicating another structure K₂NiF₄ using all the available parameters online, instead I am getting K₄Ni₂F₈.
a =b= 4.00 Å   c= 13.00 Å
α =β = γ =  90.00 º

Wyckoff   Element   x   y   z
2a               Ni   0   0   0
4c                 F   1/2   0   0
4e                K   0   0   0.354925
4e                 F   0   0   0.153956
The bulk structure of Cs₂PbI₂Br₂ follows the K₂NiF₄-type and belongs to the tetragonal space group of I4/mmm
(no. 139) with the lattice parameters of a=b=5.6385Å, c=18.879Å inwhich the lead atomis located in the core of
 octahedron, and the corners are occupied by I and Br atoms where the out-of-planeterminal site is occupied by I atoms and the in-plane bridging site by Br atoms.

Please can anyone assist?, Thank you