How to get electrode coordinates for two probe system

[dhurba]

Currently my posted script will only build homogeneous structures where the left and right electrodes are the same. It's not entirely trivial to build heterogeneous systems like the one you envision because the XY unit cells for the two electrodes must be the same, and hence stretched if the lattice constants are not the same.

As mentioned, in ATK 12.2 we're improving things a lot, I will use your system idea to test if we have made it possible to set this up easily; it's an important type of system that we should support.

Please make a script for a heterogeneous system with the functionality of inserting two different electrodes if possible  ...I am trying to manipulate the present script but not successful

Thanks in advance

[dhurba]

Secondly i am trying to get the transmission and current voltage characteristics of the following structure i have attached ..Here i have "deleted" the right electrode so as to say i have ignored the ohmic contact for the calculation..

But the calculation is taking a lot of time around 2-3 days ..Please see/Verify my Structure whether my process is correct or Wrong ..

[Anders Blom]

Yes, that's a big structure, not much to do but wait. However, you can reduce it a bit, I think at least by one layer in X and Y, there should still be enough vacuum in those directions.

Writing a general script for setting up heterogeneous structure that would work well for 11.8 is far from trivial, and that version is becoming old soon anyway, so there is no point in spending time on that. However, the structure you have is suitable to computing the interface between the metal and CNT, so you're in good shape already.

[dhurba]

Yes, that's a big structure, not much to do but wait. However, you can reduce it a bit, I think at least by one layer in X and Y, there should still be enough vacuum in those directions.

Writing a general script for setting up heterogeneous structure that would work well for 11.8 is far from trivial, and that version is becoming old soon anyway, so there is no point in spending time on that. However, the structure you have is suitable to computing the interface between the metal and CNT, so you're in good shape already.

Thanks for the reply ..one more question ..is there any way to calculate work function of carbon nano tubes .like of different chirality / diameter in 11.8 (i did not get by searching the forum)

[anir]

It is at least good if you can motivate the choice of the distance, if you don't optimize it.

Sir,
    I have the licence for EHT and I wish to optimize my Au-Cnt-Au structure as mentioned above.
    But the tutorial
    http://quantumwise.com/publications/tutorials/mini-tutorials/95-optimizing-the-geometry-of-a-two-probe-system
    suggests to use DFT,so will i have a correct optimized structure or not.....
                                                                              Thanking you in advance
   

[dhurba]

Yes, that's a big structure, not much to do but wait. However, you can reduce it a bit, I think at least by one layer in X and Y, there should still be enough vacuum in those directions.

Writing a general script for setting up heterogeneous structure that would work well for 11.8 is far from trivial, and that version is becoming old soon anyway, so there is no point in spending time on that. However, the structure you have is suitable to computing the interface between the metal and CNT, so you're in good shape already.

I increased the k points to 500 .. increased the number of history steps to 15 and beyond... also lowered the tolerance to 1e-4. still the structure is not converging .. any suggestion till which i can continue changing the above parameters ..

[Anders Blom]

I'm sorry I didn't see this before. You have a mistake in the configuration - there are C atoms in the left electrode!

The problem is that your "surface" - the Al atoms in the central region - has exactly the same size as the left electrode. This is not recommended, for many reasons; you should have at least one more layer of Al in the central region. So, you should go back to the central region, add some Al so you have at least 7 layers of Al there, 8 is better (you need 6 layers in the left electrode, I think, 4 is too little) and then remake the device with 6 Al layers in the left electrode again.

[dhurba]

Thanks it worked