Recent Posts

31

General Questions and Answers / Parallelization issues with OrbitalMoment() in QuantumATK

« Last post by corsicATK on October 25, 2025, 11:22 »

Hello everyone,

I need to calculate atom-resolved orbital moments using OrbitalMoment() in QuantumATK and obtain the values per atom and per k-point. My first question is: is it possible to directly get this information from the output?

If not, my fallback solution is to compute the function for a single k-point at a time and loop over all k-points. This works fine sequentially.

However, when I try to parallelize my code with mpi4py by distributing k-points over several ranks, I run into problems:

Deadlocks can occur during the computation.

At the end of the loop, all ranks return the same orbital moment values, even though each rank is supposed to work on a different k-point.

It seems that OrbitalMoment() does not execute independently on each rank and requires some form of internal synchronization or communication.

I would appreciate any guidance on:

Whether it is possible to obtain atom-resolved orbital moments for each k-point directly.

If independent parallel computation per k-point is possible, and how to do it safely with QuantumATK.

Thanks a lot for your help!

32

General Questions and Answers / Issue with launching simulation from SLURM

« Last post by AsifShah on October 21, 2025, 12:07 »

Dear Admin,
I am trying to launch a simulation from SLURM. It shows active status on squeue but the log file is empty for long time.
I m using latest QuantumATK X.2025.06.

Kindly help in this regard!

33

General Questions and Answers / Re: Recommended approach to generate an interface between two amorphous materials

« Last post by evansjc on October 20, 2025, 20:35 »

Hi Anders,

Great! I will try this. Thank you so much for your help!

34

Scripts, Tutorials and Applications / Re: How to Apply Heat Flux in NEMD Simulations Using the "Exchange Interval" Option

« Last post by Priyadarshini on October 18, 2025, 08:31 »

Hello QuantumATK team,

Thank you for your guidance; the process is now clear to me. I go through the reference image attached showing a temperature profile analysis for SiO₂ quartz (MTP pretrained, RNEMD) using the Molecular Dynamics Analyzer in QuantumATK.
Could you please share the official documentation or example workflow/script that explains how to set up and perform the RNEMD (Reverse Non-Equilibrium Molecular Dynamics) simulation for SiO₂ using the MTP potential and generate and fit the temperature profile as shown in this plot?

Any references or sample Python scripts for automating this process in the QuantumATK Script Generator would be very helpful.

Thank you in advance for your guidance!

35

General Questions and Answers / Re: Unexpected Transmission Channel in Monolayer Graphene DFT Transport CalculationD

« Last post by AsifShah on October 13, 2025, 14:11 »

Hi kaihuang,

Can you check with these quick fixes for the file D0_BulkDevice.py

1. Increase electrode extension.
2. Use k_point_sampling = MonkhorstPackGrid(na=12, nc=300).
3. Use medium basis set.

36

General Questions and Answers / Unexpected Transmission Channel in Monolayer Graphene DFT Transport CalculationD

« Last post by kaihuang on October 10, 2025, 22:44 »

Dear QuantumATK team,

My research strongly relies on ATK for calculating transport properties, and the LCAO framework in ATK has been extremely helpful and valuable for my studies.

Recently, I calculated the transmission spectrum of monolayer graphene. Since graphene is a well-studied material with a simple structure, it is often used as a benchmark system. However, I encountered a strange problem.


(Web image here. If it's not shown, find in the attachment.)

As shown in the figures:
- Fig.(a) presents the graphene band structure calculated using VASP along a chosen direction c. b direction has vacuum layer. The lattice has been orthogonalized, showing the well-known two Dirac cones, with the Fermi energy set to zero. ATK band-structure calculation matches this result.
- Fig.(b) and (c) show the bulk (unit cell) non-bias transmission spectrum calculated using ATK 2024. In (b), the x-axis is k-parallel and the y-axis is energy; in (c), the x-axis is energy and the y-axis is transmission. Overall, (b) looks very similar to the band structure in (a) which right, but there is one abnormal transmission channel (green line). This green channel causes the transmission at the Fermi level in (c) to be 1 instead of 0, which is clearly incorrect. The calculation was done using DFT with Dojo pseudopotentials.

To identify the issue, I tried several approaches: Using ATK 2022 instead of 2024; Rewriting the structure with cleaner fractional coordinates (Fig.(d)); Increasing the k-grid to up to 18×1×96 (Fig.(e)). None of these changes fixed the problem.

I also tried using SG15 pseudopotentials (Fig.(f)), it’s even worse that two fake conduction channels appeared (green lines).

I also tried building a bulk-like device by repeating the unit cell several times (Fig.(g)). In that case, the fake channel disappeared, but the transmission became non-integer, and the non-zero region below the Fermi level appeared as discrete lines rather than continuous bands.

Finally, I tested the Slater–Koster (method following the official tutorial (https://docs.quantumatk.com/tutorials/transmission_gr_mos2/transmission_gr_mos2.html). The result was correct and free of fake channels. However, since my main workflow is based on DFT, the S-K method is not suitable for my project. The fact that the S-K method works correctly suggests that my structure setup is fine and the problem might come from the DFT implementation in ATK.

I have attached the calculation files for both the bulk (unit cell) case (corresponds to Fig.(e)) and the bulk-like device case (corresponds to Fig.(g)).

I sincerely hope to receive your advice.

Thank you very much!
Kai

37

General Questions and Answers / Re: calculation of gate oxide capacitance

« Last post by techenthusiast on October 8, 2025, 06:26 »

I suppose you are mainly looking at how the electron density changes with bias, so you can just subtract the zero-bias electron density and that's your bias-induced charge transfer.

Dear experts,

Good afternoon, how to compute cgg, cgd, cgs  of a fet using quantum atk?

38

General Questions and Answers / how to compute cgg, cgd, cgs of a fet using quantum atk?

« Last post by techenthusiast on October 7, 2025, 11:47 »

Dear experts,

Good afternoon, how to compute cgg, cgd, cgs  of a fet using quantum atk?

39

General Questions and Answers / Whenever trying to open Current density .hdf5 file after execution isnot opening

« Last post by techenthusiast on October 6, 2025, 05:24 »

Dear experts,

Good morning, Hope you are doing well. Whenever trying to open the Current density .hdf5 file after execution is not opening.. Opening editor instead. How to open the executed result file? Thank you.

40

General Questions and Answers / Connection to Cluster

« Last post by Ruhani on October 5, 2025, 01:11 »

Hi All,
I have tried since last weeks to makea  connection to the cluster to make my simulations faster. Of course, there are a lot of steps that maybe one of them is the main reason to fail of running. But in the attachment, you can see the error I have made in the last step. Have you ever met such an error?
Regards
Ruhani Dadashov