Messages

1

General Questions and Answers / Re: About the convergence of transmissionspectrum calculation

« on: April 13, 2018, 16:46 »

Dear Petr Khomyakov,

For the same device configuration, I redid the k-point scan using ATK SE: Extended Huckel method. It's much faster than the DFT method, about 1/20 of the time consuming. However, the converged current calculated using Huckel method is different with that calculated using DFT method, seen in the attached figure: the red plot was calculated using DFT method, and the blue one was calculated using Huckel method.

I have a question: Even though that the result calculated using DFT method might be more accurate, can I use the Huckel method for the simulation of transmission spectrum? In other words, to what extent can I trust the result obtained using Huckel method?

Thank you very much!

2

General Questions and Answers / Re: About the convergence of transmissionspectrum calculation

« on: April 12, 2018, 03:27 »

Thank you very much for your valuable comments! It seems that a k-point scan or a mesh-cutoff scan should be needed even though they might take a long time for doing so. It's boring but necessary.

3

General Questions and Answers / Re: About the convergence of transmissionspectrum calculation

« on: April 11, 2018, 03:52 »

Dear Petr Khomyakov,

Thank you for your reply. I increased the kB up to 25 and got the attached figure. Do you think that kB=25 is almost sufficient for the transmission spectrum calculation?

Thanks again for your kind help!

lknife

4

General Questions and Answers / About the convergence of transmissionspectrum calculation

« on: April 10, 2018, 09:52 »

Dear experts,

I want to calculate the transmission spectrum (or IV curve) of a 2D-device using DFT-GGA method. First of all, I made a k-point scan for kB (periodic along B direction) from 9 to 19 with kA=1 and kC=150. I got the kB dependency of the transmission current, seen in the attached file.
I want to know, what kind of conclusion can I get from the figure, kB=9 is almost sufficient, or kB=19 is still not sufficient?

I appreciate you for your kind help!

5

General Questions and Answers / Re: Can anybody help me with the concept "contributions" in tranmissionpathway?

« on: March 19, 2018, 05:04 »

Thank you very much again for your kind help!

6

General Questions and Answers / Re: Can anybody help me with the concept "contributions" in tranmissionpathway?

« on: March 15, 2018, 05:04 »

Thank you very much for your valuable reply.

There are some other questions:

(1)  Since the potential of the left electrode is higher than that of the right electrode (because of the bias), the actual transport direction of the electrons shoud be from the right electrode to the left electrode. That is, the electrons originate from the right electrode and then transport to the left elelctrode.  In other words, I should calculate the transmission pathways with contributions=right.  Is it right?
If the actual transport direction for the electrons is from the right electrode to the left electrode and I calculated the transmission pathways with contributions=left, is there any problems doing like that?

(2) How to check the T_ij? There is no such parameter in the settings of the transmissionpathway in the Viewer. Do I need to check it from the text representabion of the transmissionpathway? 

(3) How to set the energy value when I set the parameters for the  tranmissionpathway calculation? Do I need to set the energy value according to the transmission spectrum? That is, to set the energy to the value when it shows relatively high transmission spectrum?
 
Thank you very much again for your kind help!

7

General Questions and Answers / Can anybody help me with the concept "contributions" in tranmissionpathway?

« on: March 14, 2018, 06:48 »

Dear experts,

I am not sure of the meaning of this sentence " The transmission pathways contributions from the left or right electrode" when I tried to calculate the transmissionpathway of a two-probe device under a certain bias.

What's the difference: contribution from left or right electrode?

Please see the attached picture. It's the transmission pathway of a in-plane hetero-junction. I don't know what's the thickness of the lines stands for.

Does  the thickness of the transmission lines stand for the magnitude of the current flow? But according to my knowledge, the current flow from one electrode to another electrode should be the same along the transport direction. I don't know why there is no transmission lines near the right electrode.

Any other explanations to the question? I forgot if I used the default setting of the transmissionpathway (contribution from left). Do I need to recalculate the transmissionpathway with "contribution from right electrode"?

I appreciate your kind help!

8

General Questions and Answers / Re: Looking for a tutorial about the Bi2Se3 thin film device

« on: March 7, 2018, 06:46 »

Thank you very much for your kind help!
By the way, why this case study is not finished yet? Any problem with it?

9

General Questions and Answers / Re: Looking for a tutorial about the Bi2Se3 thin film device

« on: March 6, 2018, 07:50 »

Dear Petr Khomyakov,

Thank you very much for your kind reply.

However, this tutorial is not the one I am looking for. Once there were two tutorials on topological insulator on the website, one is about the bulk properties of Bi2Se3 topological insulator,  the tutorial that you mentioned; the other one is about the transport properties of Bi2Se3 thin film device.  I saw the latter tutorial (a case study) last year, when it was not fully completed. Now I cannot even find this uncompleted tutorial on the website.

Can you help me with this problem? Thanks again for your help!

Best regards,
lknife

10

General Questions and Answers / Looking for a tutorial about the Bi2Se3 thin film device

« on: March 5, 2018, 14:24 »

Dear ATK staff,

I once saw a tutorial about the topological insulator Bi2Se3 thin film device on the quantumwise website. But now I cannot find it. Can you tell me where I can get to that tutorial? Also, I want to find an older version of the tutorial "mobility".

Best regards,
lknife

11

General Questions and Answers / Re: About the repeatability and correctness of the calculation using ATK

« on: January 7, 2018, 03:10 »

Dear Jess Wellendorff,

I got the result of the kscan calculation for my device, could you please have a look at it?
From the figure, it seems that the convergence of the current is mostly affected by the resolution of kB, and 100 for kC is enough, is it right?

12

General Questions and Answers / Re: About the repeatability and correctness of the calculation using ATK

« on: January 5, 2018, 04:10 »

Thank you very much for your help! I really appreciate that!

13

General Questions and Answers / Re: About the repeatability and correctness of the calculation using ATK

« on: January 4, 2018, 15:11 »

Thank you very much for your prompt reply! For the empty .py file,  I am sorry for the mistake and I have uploaded the correct one. Please help me to check it.

Thanks a lot again for your kind help!

14

General Questions and Answers / Re: About the repeatability and correctness of the calculation using ATK

« on: January 4, 2018, 10:23 »

Dear Jess Wellendorff,

Could you please help me check the attached .py file for k-point scanning? It was written according to your script with just a little modification. It was shown in the .log file that no SCF calculation was used. However, I do want to use the SCF calculation. What's wrong with the script?
In addition, there are some errors about plotting the curve. It was said "TypeError: float() argument must be a string or a number". Why?

Another problem: I cannot find the access to the Forum from the website "www.quantumwise.com" now. Is there any problem with the website?

I appreciate you for your kind help!

Lknife

15

General Questions and Answers / Re: About the repeatability and correctness of the calculation using ATK

« on: January 4, 2018, 03:15 »

Dear Jess Wellendorff,

Thank you very much for your kind help! It's really helpful! I am studying the python programming about ATK, wishing to learn more from you!

Thanks a lot again!