ATK shows the zigzag phosphorene nanoribbon to be non-metallic

[jim12565]

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.

[Petr Khomyakov]

It does not look like quasi-1D structures with the actual 1D edges to me, i.e., both structures are still 2D infinite sheets with no edges. 

[jim12565]

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?

[Petr Khomyakov]

"Correct" really depends on what you actually want to study. If your system of study is a strip of a 2D material with the actual edges, then - yes - you have to cut the edges by increasing the lattice parameter in the corresponding direction, and may or may not do passivation of the edges with hydrogen - again depending on what you want to do.

You can always visualize periodic  images by using the Repeat plugin in the Builder -> Bulk Tools -> Repeat. You will then see an array of nanoribbons, but do not forget to undo the Repeat before submitting the structure from the Builder to the Scripter.

[jim12565]

This was very helpful, thanks a lot Petr.