Topics

1

General Questions and Answers / Inconsistant transmission between bulk and bulk-like device

« on: June 2, 2024, 21:04 »

I'm calculating the transmission of a 2D material.

I tried two approaches:

1. Transmission of the bulk in the unit cell.
2. Transmission of the bulk-like device, where the left electrode, right electrode, and central area are all the same unit cell structure.

I assumed the transmission results would be identical. However, the results are different:

[image in the attachment]

(image link in case it doesn't show: https://imgur.com/wRPUPpw)

The left image shows the unit cell transmission, while the right image shows the bulk-like device transmission. Both calculations use GGA with polar spin and no SOC included.

You can observe that the transmission curves relative to the Fermi energy are different, with the transmission from the unit cell being larger.

My question is, why could this difference occur? Should the results be the same, and which one should be considered correct?

Thanks,
Kai

2

General Questions and Answers / Half integer transmission in hdf5 file

« on: April 21, 2024, 06:55 »

Hello,

I conducted the transmission calculation for a bulk system and attempted to plot the transmission concerning k by parsing the hdf5 file. In this instance, I initiated the DFT calculation, incorporating Spin-Orbit Coupling and noncollinear magnetic moments. GGA method and SG15-SO pseudopotential. Subsequently, the transmission was calculated. Within the output hdf5 file, I observed that the transmission is delineated in the data tree as follows:

- TransmissionSpectrum_0
    - transmission
        - 0
            - data
        - 1
            - data
        - 2
            - data
        - 3
            - data

For each 'data,' there is a 2D array. Two indices represent k points and energy, respectively.

However, two questions arise:

1. Is it correct that 0, 1, 2, 3 above represent the transmission of spin all, x, y, and z, respectively? Or do they represent spin all, y, z, and x? Or something else?
2. In the transmission->0->data, I noticed that the transmission plot matches the electron band structure well, which implies the validity of the result. However, I saw many half-integer transmissions, like 0.5, 1.5, 2.5, etc. It seems that each band only contributes 0.5 transmission channel rather than 1. So, I would like to inquire about the meaning of this dataset. Can I multiply it by 2 to get the right result?

Additionally, I attempted the transmission calculation without SOC, i.e., choosing just spin polarized. The transmission output in the hdf5 file is as follows:

- TransmissionSpectrum_0
    - transmission
        -0
            - data

This time, there's no spin projection. But again, each band contributes only 1 transmission channel rather than 2 (for the two spin eigenstates). Again, what's the meaning of this data in hdf5, and can I just multiply by 2?

Thanks,
Kai