Energy dependent LDOS for a benzene device

[kstokbro]

The attached figure shows the LDOS along z (averaged over x and y), for DTB coupled with gold electrodes. Note how the high density of states coincides with the resonances in the transmission spectrum. I also attach the scripts used for generating the figure.

[John]

Dear Dr. kstokbro,
      Can you give any suggestions to extract the date of the energy relevent LDOS, and then plot the Z-Energy figure by other software, e.g. origin. Another, the scale of the color bar could be helpful to understand this figure.

      Thank you.

[kstokbro]

There will be a tutorial with this within the next couple of days. The tutorial is currently being reviewed and should be ready any moment.

[John]

Thank you, Dr. kstokbro.
Another, when analysizing the Local Device Density of States, one can do it only at one energy value, whether is it possible to describe the LDOS at one optional energy range, e. g. from -1 to 1 eV. If so, the LDOS distribution (partial charge) on the real atom (atoms) can be viewed, not just the Z  coordinate.  right?

[Anders Blom]

See http://quantumwise.com/corporate/news-archive/136! About the energy range, you can easily make a script that runs over a sequence of energies, but keep in mind you get a 3D grid for each one. It's possible to project them on a particular point in space, if that's what you want. For any 3D grid, you can ask for the value of the grid in a point (x,y,z) like so:

Code: python

grid_data = LocalDeviceDensityOfStates(...)
value_at_point = grid_data.evaluate(x,y,z)

[John]

Dear Anders Blom，
   Can you give any suggestions about the PDOS,how to determine the projected atoms of the central scattering region (or only the sample molecule) ? Like the example'Au-DTB-Au', it only gave the PDOS of phenylene ring (the two S atoms not included), and compared that with the Transmission spectrum? it is similar for the analysis of eigenstates.  Thank you.

[Anders Blom]

Not sure I understand your question... You don't "determine" the projection atoms, you choose them, yourself. If you wanted the S atoms included, just extend the list of projection atoms.

[John]

Dear Anders Blom,
    I mean this new tutorial about the Au-DTB-Au system, i.e.  http://quantumwise.com/documents/tutorials/latest/MolecularDevice/index.html/chap.analysis.html#sect1.analysis.transmission
    Here, it only gave the PDOS of phenylene ring (the two S atoms not included), and compared that with the Transmission spectrum. Why not the whole sample molecule? So, I have the question how to reasonablely determine the projected atoms to analyze the transmission spectrum.
    

[kstokbro]

The reason we only include the phenyl ring, is that the electrons must pass this ring, thus it might give the simplest picture.
However,  you can also include the S atoms and analyze the device in terms of the DTB molecule, this was how it was done in our original article in CMS, and it also gives valuable insight.

There is no single way to analyze the device, you must try several different ways, and select the model which give the simplest picture.

[John]

Thank you, Dr. kstokbro.

[Anders Blom]

I have used the script, with a few minor modifications, to plot the LDOS of a quite different structure. I can't reveal the particulars, but it's a sandwich structure of two different semiconductors A-B-A, where B is a wide-gap material; the junctions are indicated by the red lines.

The white areas are as above regions of high density of states, i.e. the non-white regions indicate the band gap. Thus we here get an atomic-scale illustration of the band bending and band alignment of a heterojunction, and we can follow (sort of) how the top of the valence band and the bottom of the conduction band behave as a function of the Z coordinate.

[Parveen]

The attached figure shows the LDOS along z (averaged over x and y), for DTB coupled with gold electrodes. Note how the high density of states coincides with the resonances in the transmission spectrum. I also attach the scripts used for generating the figure.

i was trying same for 1.6V but didn't get much success. so far i was changing left electrode and right electrode potentials in new calculator. is there anything else that i can do to get the LDOS image at 1.6V?