Transport properties for Optimized Structures

[Nemthianhoi Zou]

Hello everyone,

I’m facing an issue when trying to convert a bulk structure into a device for transport property calculations. I can successfully perform the bulk-to-device conversion for the original (unoptimized) structures. I want to apply pressure on the material and calculate the transport properties which is an available feature in the "Optimize Geometry" block. However, after geometry optimization, I’m unable to convert the optimized structure into a device.

Could you please explain why this happens and how I can convert the optimized structure into a device?

Note:     Ori.png: Original structure>Surface Cleave (Thickness=5)>Device from Bulk
Optgeom1.png: Optimized Structure>Surface Cleave
Optgeom2.png: Surface Cleave (of Optimized structure)>Device from Bulk

Additionally, I’d like to know how to calculate the transport properties of amorphous materials, and what would be an maximum number of atoms to use for such calculations.

Thanks in advance for your help!

[AsifShah]

Hi
This happens because QATK does not recognise the atoms in your electrode (left and right end) as repetitive after geometry optimization.
A way around is to use tag on few layers of atoms on left/right end and keep them fixed during optimization of central region but be careful this may introduce internal strain.
A better is way is to fix left side atoms of your material and keep right side atoms as rigid. Also, put a vacuum on the right side so that the rigid atoms can move into vacuum for proper relaxation. Then post relaxation remove vacuum using fit cell and you can easily create device.