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How to find the dynamic capacitance of a nanowire in ATK?

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serhan:
Dear users,

Is it possible to calculate the dynamic capacitance of a nanowire or any other two-probe system in ATK?

I think, we can use C=Q/V formula.

* Can we extract Q(r) and V(r) (r being the 3-D posisiton vector, Q(r) being the 3-D charge matrix and V(r) is 3-D potential matrix of the scattering region) from the output file with extension .vnl  to another tool such as MATLAB? (I tried to read .nc file using a NetCDF reader but it was not straight :( )

If we can extract Q(r) and V(r) by simple element by element division I think a reasonable capacitance can be obtained. Also, it may be done with some NL coding  ;) But extracting to MATLAB or sth else is also interesting I think.

Regards and nice Christmas and New Year :)

Serhan

Nordland:
Hey!

I tryed cooking something together. It is done such that you give it your calculation as a netcdf file. You simply modify the script to have the correct filename
of your calculation, and then you give it the output file and then it will calculate the "dynamic capatitance" by using the formula from above
and store it a VNL file. I have attached the script, and created a plot of it in 2D, since it is easy to see things this way that in 3D if you ask me :)
Whatever the results are correct or not - that I don't know :)

For this Li-H2-Li wire which I tested on, it seems that the averaged dynamic capatitance is zero?


I am not soo used to matlab, but getting the data to xyz file is not a problem at all.

P.S It should be noted that I have given it the unit Ry despite the units is really Ry*Bohr**(-1.5), but in order to save as a Local potential I have tricked it a bit :)
The values are correct - just ignore the Ry.

serhan:
Hi Nordland,

Your answer and attached script is excellent, thank you very much!  :)

We can plot the simulation outputs for example electron density and potential profile in 3-D in VNL easily , Ok, it is very well.  ;D

But, can we export these 3-D outputs to a simple file that can be read by any other math tool, for example to a xyz file such as:  ???

X coordinate        Y coordinate        Z coordinate       Electron density
1E-10                      1E-10                 1E-10               0.02
2E-10                      1E-10                 1E1-0               0.015
.                             .                         .                      .
.                             .                         .                      .

Thanks again...

Serhan  ;)

Nordland:
Well you ask for it :)

You can find it here.

serhan:
Thank you very much!  ;D

Regards

Serhan

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