electrode_voltages = (0.0,0.0)*Volt
Left | Scattering region | Right
Li Li Li Li | Li Li Li Li H H Li Li Li Li | Li Li Li Li
Yes, the Li-H2-Li is symmetric, and so should the voltage drop be, but it is a matter of convergence, if the tolerance is low!
I offer some calculation examples of voltage drop.
All calculations were done with the algorithm "ElectrodeConstraints.DensityMatrix".
As Nordland mentioned above, "ElectrodeConstraints.DensityMatrix" instead of "ElectrodeConstraints.Off" should be used when you calculate the voltage drop.
But in some cases such as "Au-DTB-Au", you might get less convergence of SCF with "ElectrodeConstraints.DensityMatrix" (More correctly, the electronic structure that seems to be strange is obtained).
Then, you had better use "ElectrodeConstraints.RealSpaceDensity" instead of "ElectrodeConstraints.DensityMatrix".
I regard your voltage drop as qualitatively the same as mine.
Perhaps the quantitative difference comes from k-point sampling.
I couldn't find out the script used for the calculation in my hard disc, so that I'm not sure precise k-point sampling in my calculation.
However, it would probably not be (10,10,10) but like (6,6,100).
I offer some calculation examples of voltage drop.
All calculations were done with the algorithm "ElectrodeConstraints.DensityMatrix".
As Nordland mentioned above, "ElectrodeConstraints.DensityMatrix" instead of "ElectrodeConstraints.Off" should be used when you calculate the voltage drop.
But in some cases such as "Au-DTB-Au", you might get less convergence of SCF with "ElectrodeConstraints.DensityMatrix" (More correctly, the electronic structure that seems to be strange is obtained).
Then, you had better use "ElectrodeConstraints.RealSpaceDensity" instead of "ElectrodeConstraints.DensityMatrix".
I have been build all the two-probe system as you post, but I could't get none of the beautiful pictures of voltage drop as your examples,where is my problem?
I have been notice the use of "ElectrodeConstraints.DensityMatrix" instead of "ElectrodeConstraints.Off" when I calculate the voltage drop.
The append files is my au(111) scripts and outputs,all computation performed in VNL 2008.10.
;D ;D ;D I have been modify the scripts that upload before because the wrong monkhorst_pack_parameters,but also the same results. And upload the modified scripts and results.
I also test the FFT methods,but also the same results,and I can't get nori's beautiful image!Why?
Hey everyone.
I just thought I wanted to share with you a small script for calculate the voltage drop using two selfconsistent calculations
on a twoprobe device.
The usage is straight forward:
1) perform a calculation of a twoprobe at zero bias and store the results in a netcdf file.
2) Do the same for the finite bias, and store this in another netcdf file.
3) Modify the script to match the names of your two calculations, and run it using atk voltagedrop.py.
Then you are done, and you will recieve the voltage drop in a VNL file for visualization in VNL and the
average voltage drop will be printed to the screen. Alternative you can pipe the screen into a log file and plot it using fx GNUplot.
I have attached the script and I have attached a graph showing the voltage drop calculated using this script for a Li-H2-Li system.