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Some questions about electric transport calculations
Date: 2023/09/08 16:21
Name: Ye Zhang   <lzddyouxiang@gmail.com>

Dear developers,

I have some questions while studying electric transport calculations.

(1) The figure 40 from https://www.openmx-square.org/openmx_man3.9/node127.html .At an energy range of -7.5 eV to -3.6 eV, the transmission rate is 0. Does this mean that the forbidden band of this carbon chain is between -7.5 eV and -3.6 eV, with a bandgap of approximately 3.9 eV? And the unit of vertical axis transmission is 1/spin, what does it represent and what is its physical meaning?

(2) In https://www.openmx-square.org/openmx_man3.9/node128.html , it say when change the order of the lattice vectors, please make sure that the keyword 'scf.Kgrid' has to be changed as well. However, in 'work/negf_example', the order of the lattice vectors for Lead-L-8ZGNR-NC.dat and Lead-L-8ZGNR.dat has changed, but the keyword "scf. Kgrid" has not changed.

(3) I want to obtain the electron mobility. Can I use the k-resolved conductivity obtained from the electric transport calculations to calculate the electron mobility? If so, how should I calculate it?

Best regards,
Ye Zhang
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Re: Some questions about electric transport calculations ( No.1 )
Date: 2023/09/13 12:05
Name: T. Ozaki

Hi,

> (1) The figure 40 from https://www.openmx-square.org/openmx_man3.9/node127.html .At an energy range
> of -7.5 eV to -3.6 eV, the transmission rate is 0. Does this mean that the forbidden band of this
> carbon chain is between -7.5 eV and -3.6 eV, with a bandgap of approximately 3.9 eV?

In the band structure, there is the corresponding band gap, which can be confirmed
by calculating the band structure. 

> And the unit of vertical axis transmission is 1/spin, what does it represent and what is its physical meaning?

This means the transmission per spin channel.


> (2) In https://www.openmx-square.org/openmx_man3.9/node128.html , it say when change the order of
> the lattice vectors, please make sure that the keyword 'scf.Kgrid' has to be changed as well.
> However, in 'work/negf_example', the order of the lattice vectors for Lead-L-8ZGNR-NC.dat and
> Lead-L-8ZGNR.dat has changed, but the keyword "scf. Kgrid" has not changed.

Please make sure that the system is one-dimensional, and no k-dispersion for the b-c plane.
"scf.Kgrid  201 1 1" means that the k-dispersion is taken into account along the a-axis 
for the calculation of lead part.

> (3) I want to obtain the electron mobility. Can I use the k-resolved conductivity
> obtained from the electric transport calculations to calculate the electron mobility?
> If so, how should I calculate it?

The k-resolved transmission is available, and how to get is explained at
https://www.openmx-square.org/openmx_man3.9/node131.html
which might be utilized to calculate the electron mobility.

Regards,

TO
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