Messages

1

General Questions and Answers / Re: How to optimize the geometry of a Silicon nanoribbon?

« on: August 17, 2018, 08:52 »

OK, thanks Petr.

2

General Questions and Answers / How to optimize the geometry of a Silicon nanoribbon?

« on: August 15, 2018, 20:01 »

Hi

I have formed a silicon nanoribbon with the bond length of 2.2A and buckling of 0.43A as given in various papers. However I don't know how to optimize this geometry, i.e. selecting the k-point sampling and setting the optimize geometry part, especially in which coordinates (x, y, z) to constrain the cell? I'd be glad if you help about this question please.

P.S. I have attached the silicon nanoribbon unit cell to this post.

Best regards
Jimmy

3

General Questions and Answers / Re: NDR in phosphorene nanoribbon

« on: July 9, 2018, 07:31 »

Dear Petr,

I calculated the bandstructure as you said but it is nowhere similar to the one given in the paper as attached. What can I do to correct my simulation, or is mine correct with ATK and there may be a problem with the paper?

Thanks a lot.

4

General Questions and Answers / NDR in phosphorene nanoribbon

« on: July 7, 2018, 12:59 »

Hi,

I recently tried to replicate the I-V curve given in the paper given here https://www.researchgate.net/profile/Chenhui_Zhang3/publication/274730808_Homostructured_negative_differential_resistance_device_based_on_zigzag_phosphorene_nanoribbons/links/554a0efd0cf29ff75c75edd2/Homostructured-negative-differential-resistance-device-based-on-zigzag-phosphorene-nanoribbons.pdf?origin=publication_detail.

The I-V curve is the (Fig. 3a) (attached) which corresponds to the phosphorene nanoribbon structure given as Fig. 1 in this paper (also attached). They used Transiesta package while I'm using ATK 2015. I tried the simulations with their parameters as written on the paper but the results of ATK seems not to be same as described in the paper (attached). (I also attached our ATK input file).

ATK results have the peak at around 0.3V (compliant with the paper) but goes to zero as the voltage is increased (not compliant with the paper, their result goes to something around 10uA~20uA but never zero).Could you give me any idea what I might be doing wrong so that I can replicate the results of this paper? (Note: I used different vacuum lengths all greater than 15 Angstrom).

Cheers

5

General Questions and Answers / Re: ATK shows the zigzag phosphorene nanoribbon to be non-metallic

« on: June 12, 2018, 15:21 »

This was very helpful, thanks a lot Petr.

6

General Questions and Answers / Re: ATK shows the zigzag phosphorene nanoribbon to be non-metallic

« on: June 12, 2018, 06:10 »

Thanks again Petr. Do I need to increase the a vector to isolate this structure from its invisible images for obtaining a correct 1D nanoribbon?

7

General Questions and Answers / ATK shows the zigzag phosphorene nanoribbon to be non-metallic

« on: June 9, 2018, 09:36 »

Hi. I have tried to build armchair and zigzag phosphorene nanoribbons and simulated them in ATK. I considered the paper given on https://arxiv.org/ftp/arxiv/papers/1405/1405.3348.pdf which says that armchair phosphorene nanoribbons are semiconducting while zigzag phosphorene nanoribbons are metallic. I used the phosphorene bulk structure given by Dr. Khomyakov in this post: https://quantumwise.com/forum/index.php?topic=5757.0 and got the nanoribbons by cutting them in the appropriate directions (I hope I did it right). As you can see from the attached first figure, the armchair phosphorene nanoribbon seems to be semiconducting as implied by the reference paper. However, the zigzag phosphorene nanoribbon gives the IV plot of figure 2 which is insulating and it is supposed to be metallic according to the reference paper. I have attached the input files of both armchair and phosphorene nanoribbons for your information. Is there anything wrong with the simulation parameters of the zigzag nanoribbon that makes the results incorrect? I hope you can give a hint about this. Thanks to all. Cheers. Jim.

8

General Questions and Answers / Re: I-V curve of original GNR and GNR cut from graphene sheet

« on: June 6, 2018, 05:59 »

Thanks for your fast reply Petr. So as a general rule, should I increase the lattice's B vector (something like 2 times) whenever I cut nanoribbon from a sheet structure?

9

General Questions and Answers / I-V curve of original GNR and GNR cut from graphene sheet

« on: June 5, 2018, 15:33 »

Hello again, I have simulated a 10 atoms wide zigzag graphene nanoribbon built from the nanoribbon builder and then simulated the (same?) GNR cut from the graphene sheet. The I-V curve of the original GNR is sort of sensible as attached but the I-V curve of the GNR cut from the graphene sheet seems incorrect as attached. When I visualise each structure in the Viewer, they seem the same as you can also see in the attachment. What can cause this difference of their I-V curve being different, or I could ask if the GNR cut from the graphene sheet is not perfectly right for som reason? Cheers, Jim.

10

General Questions and Answers / Re: The crystal builder tutorial

« on: June 4, 2018, 10:43 »

Thanks a lot. Jim.

11

General Questions and Answers / Re: The crystal builder tutorial

« on: June 4, 2018, 10:15 »

Thanks for your reply, Peter. Is it possible to share the correct structure here  Cheers, Jim.

12

General Questions and Answers / The crystal builder tutorial

« on: June 3, 2018, 09:47 »

Hello. I followed the crystal builder tutorial (given on https://docs.quantumwise.com/tutorials/crystal_builder/crystal_builder.html) and got different results compared to the ones given in the tutorial. I've attached the bandstructure I got from ATK 2017.2 and also attached the input file I generated following the tutorial. I hope somebody can show what I did wrong when building the structure or setting the simulation parameters. Or I wonder if it is possible to download the simulation input file or the geometry file of this tutorial from somwhere.. Cheers, Jim.