the transimission spectrum in a two probe system

[yangzw1985]

Hi, everyone!
     I want to calculate the transimission spectrum for a li-zno-li two probe system. But all of the coefficients are zero when I set 200 energies and the points from -12 to 12 !! when I set the energies 5000 and points from -100-200, some results is not zero appear in the area 150-200 points, but it was very small.
     The parameters for the method menu are as follows:szp,2x2x50 for brillouin zone,mesh cut off 100Ry,LDA.PZ, Tolerance 1e-004,100 points and 100Ry cut off for the two center integral. Is there anything wrong?
     Can anyone give me some suggestions on " how should I set the parameters in order to get the right transimission spectrum?".
       Thanks very much！

[Nordland]

It appears your system has converged to zero charge, if the transmission is zero for all energies.

I can try to help your own, but I need a geometry or a hint of the geometry to try out a few things....

Is it a wire or ?

[Nordland]

Do you by any chance have the log output for the selfconsistent part of the calculation?

[yangzw1985]

Attached geometry structures have been optimized. Distance between the electrodes and zno nanowire was determined by calculating the total energy to min.

[yangzw1985]

Hi,Nordland, Attached is the liznoliclusterwur72(1V) script and results. I think this may be useful ! Is there something inappropriate ?
Thank you!

[Nordland]

I only have one computer and along queue of fun calculation, but it is grinding at the problem, so I dont have a final answer for you,
but I got an idea what went wrong for you, since the contour parameters was perhaps not conservative enough you might have lost all
the electrons of the system, and hence there is no transmission for any energy.

As soon as my computer has ended the calculation, and converged to something meaningful I will report it here

[yangzw1985]

Hi,Nordland!I really need your help to check out this problem.I want to know what is the reason for the results? have you got enough time to solve this problem?

[yangzw1985]

Hi,Nordland! If you have checked out the reasons for this problem,please tell me as soon as possible. I really need your help to solve the problem?
thanks!

[Nordland]

Hey Yang.

I will try to take a look at it, as soon as my calculations on graphene ribbons ends

[yangzw1985]

Thank you!

[yangzw1985]

Hi,Nordland!

Have you finished your calculation on graphene ribbons? I want to know when you will free to help to check out this problem. Because I have tried lots of methods to solve this problem, but the results are unreasonable. I really need to solve this problem as quickly as possible, I hope you can help me to change the situations .

Thank you  very much!
   
I have been looking forward to hearing your good news!

[Nordland]

Okay, I am trying to do a couple of runs right now.

You should not change the default values for the twocenter integral values. It only leads to bad behavior.
So those I have modifed back to default values.

You should also always try zero bias first, since it is more stable and faster to obtain a good idea about which parameters to use for this system.

I have also tried to double the electrode length, and made some minor modifications and tunning of the parameters.

I will post once the calculations are done.

[Nordland]

The calculation is taking quite long!

I have attached the script here for you to try it - I have modified parameters into somewhat more reasonable values.

[yangzw1985]

Hi,Nordland!
I have tried the calculation with different parameters, attached is the calculated results!
As we can see from the log out file, if the results are reasonable, the Fermi Energy =   -0.39002 Ry for left and right electrodes. For the two probe model,the Fermi Energy =   -0.34528 Ry .
 The transmission coefficient is 0 from -12 to -2.23. This means the the transmission coefficient is 0 for the fermi level. How can I explain this?
And in the bias window [-1,1], is the transmission coefficient right?
what's more, I also can not distinguish where is the electrode and where is the nanowire.If it does not contain the electrode, why? I have read lots of papers, and the transmission spectrs shoud be divided in to three parts:left electrode, center scattering region, right electrode.
Thank you !

[Nordland]

Trying to answer the questions as best as I can.

1) When you calculate the transmission spectrum, the transmission spectrum is shifted, such that the E=0 corresponds to the fermi level (-0.34528 Ry in your case)

2) In your case the transmission coefficient is roughly 0.05 - 0.10 around the fermi level, hence there is transport at the fermi level.

3) If the transmission does not look unphysical, so the transmission spectrum is properly correct. However it should be noted, that it is not exactly a bias window you are looking at when you are looking at the transmission spectrum. It is the transmission probability for a given energy. It is true that this can be related to NON-responsive current calculation.

4) I might be wrong, but I have never seen a transmission spectrum divided into spatial regions, as it is not part of the standard formulation of the problem.
Do you have reference for a paper where this division is done?