Show Posts

This section allows you to view all posts made by this member. Note that you can only see posts made in areas you currently have access to.


Messages - AsifShah

Pages: [1] 2
1
General Questions and Answers / Electrode Sizes fixed to mininal size
« on: Yesterday at 12:47 »
Dear Admin/Others,
When doing device from bulk, it chooses minimal electrode length as one atom. However, I want to keep 2 or 3 atoms as my electrode I tried changing +/-  as shown in attachment, also tried changing left & right values below (see attachment) & electrode extension length but it does not help change the electrode length & keeps it fixed as one atom. How to rectify it? I found that changing left & right values below had no effect on the electrode size. Kindly help.
Check the attachments below.

(The reason why I want to change it to 2 or 3 atoms is because in electrode validator it says large matrix elements error & asks to increase electrode size)

2
General Questions and Answers / Bandstructures
« on: Yesterday at 11:28 »
Dear Admin/Anyone,
Could you kindly explain why any multiple of 3 chosen for a supercell (in this case for moS2) produces a different bandstructure than other sizes. It can be seen below that for a supercell of 3x3 & 9x9 we have VBM & CBM along G point whereas for other sizes such as 4x4,5x5 it is along KM points?
 Is it something with software or I am missing something here?
See the attachment below


3
General Questions and Answers / Re: convergence problem
« on: June 21, 2022, 14:17 »
You need to increase it thats the only way. I faced same issue some time ago but got results.
Try 300 maybe

4
General Questions and Answers / Re: convergence problem
« on: June 21, 2022, 14:11 »
If you are using Semiempirical calculator, then in that go to iteration control & if you have unticked no scf iteration then below it there will be maximum steps written as 100, change it to 400 & recompute. I am not sure but there is a way I guess to recompute only not converged points instead of rerunning whole calculations.

5
General Questions and Answers / Re: convergence problem
« on: June 20, 2022, 14:39 »
I see you are using Gold (as electrode I guess). From my experience with Gold adsorption calculations they taken long to optimize (converge). I normally run from command line & not from user interface & I see two files apart from .py during run. One is log file & another is name something like optimizationxxxxxx.log . Most infiormation of optimization were found in this optimizationxxx.log file.

6
General Questions and Answers / Re: convergence problem
« on: June 18, 2022, 12:00 »
Sometimes it doesn't converge because K points are not enough. 1x1x1 could be one problem. Check log file and save it then run with higher k points for same time & compare two log files to see if K point convergence is the issue

7
General Questions and Answers / Re: convergence problem
« on: June 18, 2022, 09:28 »
Depending on number of k points & size of device, transport calculations usually take long time.

8
General Questions and Answers / Hydrogen Molecule Dissociation energy calculation
« on: June 14, 2022, 14:56 »
I am calculating the dissociation energy of Hydrogen molecule.
The formula used is E(disso)=E(H2)-2E(H)
where E(H2) is the total energy calculated using two methods as:
1. Spin unpolarised/polarized using B3LYP functionals giving energies - 32, -32 respectively.
2. Spin unpolarised/polarised using PBE functionals giving energies - 31.651, -27.181 respectively.
Since H2 is spin unpolarised molecule & when choosing unpolarised/polarised using B3LYP both give same energy -32 which makes sense but why does PBE give different results for spin polarised & spin unpolarised?

9
General Questions and Answers / Re: charge transfer calculation
« on: June 9, 2022, 18:22 »
It is okay. I suggest to read some literature on Mulliken charge as it is not reliable in some cases & some people report other methods. For intro look into "Chemlibre Mulliken Charge" in Google.

10
General Questions and Answers / Re: job manager is not working
« on: June 9, 2022, 18:20 »
I would suggest use 'atkpython filename' from terminal instead.(Quotes Ignored)

11
General Questions and Answers / Re: charge transfer calculation
« on: June 8, 2022, 14:35 »
Firstly, I doubt the charge on C & O after adsorption because oxygen is more electronegative than carbon so charge should be flowing to oxygen from carbon but maybe I am missing something here. Recheck it else NVM.
Secondly, If CO charge charge has reduced it means AGNR has taken some charge from CO, (Here I suggest to see electron density 1D plot & see the minimum electron density in bonding region which should give u idea of how much CO is interacting with AGNR. It looks the charge transfer is not much happening here.

12
General Questions and Answers / Re: Simultation of Quantum Dots devices for Quantum Computing
« on: June 7, 2022, 14:50 »
Dear mariosimoni,
Yes, I if you want to just calculate energies then it should be possible to do it. NEGF would be more comprehensive & detailed though time expensive I guess.

13
General Questions and Answers / Re: charge transfer calculation
« on: June 7, 2022, 14:40 »
You will need to compare it with pristine case. Eg in normal conditions carbon has ideal charge of 4 & hydrogen has 1 & oxygen has 6 so on.. Now u can check which atoms in ur current file have changed their charge & compare it with the ideal charge.

14
General Questions and Answers / Re: how to calculate atomic charge
« on: May 26, 2022, 15:59 »
From the Mulliken Charge file I see there is no difference from ideal values. Probably your source file .py has something wrong. If possible you can share your .py file.

15
General Questions and Answers / Re: Simultation of Quantum Dots devices for Quantum Computing
« on: May 26, 2022, 15:57 »
Once you are done with bringing potential from say sentaurus? What simulation you would carry out on QATK? Will you be using NEGF? If so then I guess you want to use U (potential) into the NEGF equations which I think is not a good method because normally you require self consistent solution of NEGF with poison equation to arrive at final solution. So you will require to extract charge from NEGF into sentuarus & back potential from sentuarus into NEGF until convergence is achieved which I think is not possible to do or is challenging to do unless both devices on sentaurus & QATK resemble to one another.

PS: THis is just a hypothesis , do let me know if there is a way around.

Pages: [1] 2