QuantumATK Forum

QuantumATK => General Questions and Answers => Topic started by: Brave on March 18, 2013, 13:47

Title: Building CNT-CNT junction.
Post by: Brave on March 18, 2013, 13:47

Dear Reader,
I want to build a metallic CNT-CNT cross junction device using the builder module present in the VNL (Ver 12.8 )
However I have no clue as to how one should proceed.
Kindly suggest appropriate approaches or inform of tutorials if available.

(The structure I am trying to build is of the type : http://farm9.staticflickr.com/8250/8568652796_48ebcb5057_b.jpg (http://farm9.staticflickr.com/8250/8568652796_48ebcb5057_b.jpg))

Title: Re: Building CNT-CNT junction.
Post by: Brave on March 20, 2013, 12:58

Dear reader,
I was able to solve the problem I had mentioned earlier and was able to build a CNT-CNT junction; however am unable to define the device electrodes.
The problem reported is, the atomic position mismatch between the central region and the left electrode region.
(The screenshot: http://farm9.staticflickr.com/8237/8573593859_b531eba5b8_h.jpg (http://farm9.staticflickr.com/8237/8573593859_b531eba5b8_h.jpg))

I have approached this by translating the entire structure by the difference between the 'current' and the 'required' coordinates.
But this does not solve the problem. 
Kindly suggest some approaches.
 
   

Title: Re: Building CNT-CNT junction.
Post by: zh on March 21, 2013, 02:31

Because the requirement for the periodicity boundary condition of electrode at the current implementation of Virutal NanoLab, I think that it may not be achieved to do what you want.

Title: Re: Building CNT-CNT junction.
Post by: Anders Blom on March 21, 2013, 11:16

It can actually be achieved - sort of. But you have to be tricky, and you cannot simulate a single junction - you need to have 2. See attached picture!

Title: Re: Building CNT-CNT junction.
Post by: Brave on March 23, 2013, 15:29

So basically, I will be able to define such junctions as long as I keep the axis of the cnts perpendicular to the xy plane. Right?

Title: Re: Building CNT-CNT junction.
Post by: Anders Blom on March 24, 2013, 22:19

There is a fundamental requirement in ATK that the transport must be along C and that the central and electrode unit cells spanned by the three cell vectors are aligned such that C is parallel to Z and the AB plane is perpendicular to Z (C). So as long as you stick to that, you can define junctions like the one I depicted since it obeys the rule.