QuantumATK Forum

QuantumATK => General Questions and Answers => Topic started by: Yu Hailin on January 22, 2011, 15:35

Title: The calculation of conductance.
Post by: Yu Hailin on January 22, 2011, 15:35

Dear all, the follow method to calculate the conductance  for two-electrode system is reasonable?

The method include:
i. calculate the transmission spectrum at zero bias.
ii. using the calculated transmission spectrum to calculate the conductance at different electrode_voltages, such as:

conductance = TransmissionSpectrum.conductance(electrode_voltages=[0,0.1]*Volt)
print conductance

conductance = TransmissionSpectrum.conductance(electrode_voltages=[0,0.2]*Volt)
print conductance

......

Or it is necessially to calculate the transmission spectrum at different bias before calcualte the conductance?

Thanks in advance!

Title: Re: The calculation of conductance.
Post by: zh on January 23, 2011, 09:34

To get more accurate results, you had better do the calculation of transmission spectrum for each bias voltage. More detailed information can be referred to here:
http://quantumwise.com/documents/manuals/latest/ReferenceManual/XHTML/ref.transmissionspectrum.html

Title: Re: The calculation of conductance.
Post by: Anders Blom on January 23, 2011, 22:37

As ZH says, if you do not recalculate self-consistently you will not get as accurate results. As the manual says (http://quantumwise.com/documents/manuals/latest/ReferenceManual/XHTML/ref.transmissionspectrum.html), if you give voltages to the conductance method, it will use them and compute the conductance using the zero-bias (or whatever bias used to compute the transmission spectrum) instead of the actual transmission spectrum at the desired bias.

So, it's a quick and dirty approximation to the real calculation, and if the transmission does not depend strongly on the bias (often it does, however), the results are rather good (but there is no guarantee).

Btw, the same approach is available for the current.