Messages

1

General Questions and Answers / Re: Calculating HOMO-LUMO energies at different bias voltages in molecular junction

« on: June 26, 2017, 13:15 »

thanks for reply ... yeah i have calculated transmission spectrum at different bias voltages and there is consederable broadening of molecular levels but how can i deduce HOMO and LUMO energies from that transmission spectrum plot at different bias voltages....?? coz molecular energy spectrum analysis block gives orbital energies only at zero bias and my purpose is to tabulate orbital energies w.r.t bias voltage.

2

General Questions and Answers / Calculating HOMO-LUMO energies at different bias voltages in molecular junction

« on: June 26, 2017, 10:04 »

kindly respond about how to find orbital energies or plot molecular energy spectrum at different bias voltages

PFA table showing orbital energies as a function of bias voltages.

3

General Questions and Answers / Re: speeding up my Silicene nanoribbon geometry optimization process in ATK-DFT

« on: September 24, 2016, 08:56 »

is the reason for taking too much time while optimizing is greater bond length for SINR? If yes, what can i do to bring atoms closer?
also i went through many papers where people mentioned "region between dashed lines represent prime periodic cell under simulation". what does it signifies??? di need to perform optimization of that primitive cell only?? and then repeatind thar optimized structurein the builder??? as of now i m not doing like this...
currently i am going like
add->plugin->nanoribon->si-si(bond length=2.25)->repeating unit cell in z-direction->doping/functionalization->introduce buckling-> sen to script generator and so forth..am i doing the right way or missing something...

4

General Questions and Answers / Re: speeding up my Silicene nanoribbon geometry optimization process in ATK-DFT

« on: September 24, 2016, 08:05 »

here is my script..plz tell how can i minimize my geometry optimization run time.....

5

General Questions and Answers / speeding up my Silicene nanoribbon geometry optimization process in ATK-DFT

« on: September 22, 2016, 09:29 »

whenever i try to optimize SINR geometry it takes too much time compared to GNR and BNNR. what can i do to speed up this? And if i perform doping in it , bond with those doped atoms disappears!!! any suggestion from side would be highly appreciated...

thanks

6

General Questions and Answers / building atomic chain lets say carbon chain

« on: September 21, 2016, 08:58 »

i am new to atk.so plz let me know how can i build atomicchain in atk-vnl. As i am working on nanoribbons and attaching atomic chains to device.

7

General Questions and Answers / Re: building a graphene nanoribbon and optimizing its geometry using atk-dft

« on: September 15, 2016, 14:35 »

thankyou so much for your help... infact now i tried bringing forces down as per your advice and i got the results...now will do the same for doublezeta polarized basis set...but it took 34 steps converging in 1 hr 45 minutes ...

8

General Questions and Answers / Re: building a Silicene nanoribbon and optimizing its geometry using atk-dft

« on: September 15, 2016, 08:33 »

thanks for your valuable suggestions sir.

 plz let me know how can i change Si-C bond lengths in the builder, which you suggested,  from beginning as i started with building Z-SiNRs with Si-Si bond length 2.25 and then replaced Si atoms in one zig-zag chain by carbon atoms.
also i can not see any option in optimizer window to disable stress tolerance.how would i disable it then? i have licenced atk 13.8.0 on my desktop and atk 2016.0 release on 15 day trial on my laptop.

9

General Questions and Answers / Re: building a silicene nanoribbon and optimizing its geometry using atk-dft

« on: September 14, 2016, 16:32 »

is it possible to use too few k-points in c-direction for my work as in all the related papers in the literature people went for 50 to 100 k-pts in order to get accurate results. do we go for different k-pts for geometry optimization vs analysis.
with that sent script my forces were going like 4.12ev/angstrom->2.27ev/angstrom->2.25ev/angstrom and goes on and on with oscillatory character taking too much time. Is is good enough if i would go for fewer k-pts for optimization.
with so many k-pts analysis is not taking too much time without doing geometry optimization. main problem is with optimization only.plz help me out.

kindly check my log file as well.

thanks for frequent replies

10

General Questions and Answers / Re: building a Silicene nanoribbon and optimizing its geometry using atk-dft

« on: September 14, 2016, 15:49 »

this is the script which i have prepared. also i introduced buckling by pressing rattle tool few times.kindly suggest me if i am wrong somewhere as the main problem which i am facing is in geometry optimization using DFT. I followed the same procedure mentioned above  for building bulk  pristine Z-SINR before trying optimization of C-chain doped Z-SINR(Bulk)but same problem came in its optimization. Currently I am concentrating on bulk ribbon's properties. Then i would go for device level transport properties. plz suggest me the right way. while running the forces are not converging and this convergence is showing oscillating behavior thanks

11

General Questions and Answers / building a graphene nanoribbon and optimizing its geometry using atk-dft

« on: September 14, 2016, 13:13 »

I have tried building zigzag-silicene nanoribbon in this way:
add->nanoriboon->replaced carbon atomsby silicon and changed bond length to 2.25 from default 1.4086 for carbon.and then selected 8 atoms wide->and repeated it 3 times-> then sent it to script generator and optimized its geometry using atk-dft but calculation did not converge at all ...algo i tried c-chain doping in it but i can't see some newly formed c-si and c-c bonds in the structure. plz let me know if i am doing it the right way or missing something.

thanks