different transmission for unit cell and device

[Nayab Shiraz]

As per my knowledge, transmission spectrum for a perfectly periodic structure can be calculated just from the bulk material (unit cell) and does not need device setup. However, in order to see eigenvalues and eigen states device set up is necessary. I am trying to calculate transmission of carbon nanotubes adsorbed with metal chains. However, when I calculate the transmission spectrum using the unit cell bulk material it gives different values and when I set up device by repeating the same structure and converting it to device, it gives different values. Please guide me which one is the correct procedure to calculate transmission spectrum?

[Daniele Stradi]

Hello,

what do you mean by different values? The first thing to be check is the consistency between the transmission spectra calculated with the two methods. This is because the calculation of the transmission spectrum is done using two different methods depending on whether one uses a BulkConfiguration or a DeviceConfiguration.

Could you paste the transmission spectra calculated for the BulkConfiguration  and DeviceConfiguration, together with the scripts used for those calculations?

Best,
Daniele

[Nayab Shiraz]

I have attached the relaxed geometry of unit cell and the transmission spectra obtained for unit cell and device.
Device is made by repeating the unit cell 10 times along C direction. GGA with k points (1,1,100) is used for calculation of transmission spectra in both the cases.

[Nayab Shiraz]

Here are the scripts for calculating transmission spectra.

[Nayab Shiraz]

I would be thankful if someone can please respond to this.

[Petr Khomyakov]

Your issue might be related to a bug in computing transmission from bulk configuration calculations. We are currently investigating this. I suggest doing transmission calculations using device configuration (even for perfect bulk material) to avoid any issues. 

[Nayab Shiraz]

Thank you so much for the response.