Molecular Energy Spectrum

[karn]

Hi,Everyone

Hope you are grand. I have obtained MolecularEnergySpectrum at 0 bias voltage for a MTJ in Parallel Configuration(PC) and the results(and py file) are attached here. I actually intend to calculate HOMO and LUMO energy-level at 0 bias for spin-up and spin-down carriers for this MTJ in PC but I can't seem to understand the results I have got(I hope this is the right way to find HOMO and LUMO). I seek your advice on how to find HOMO and LUMO for spin-up and spin-down carriers from these results and also what do the 3 columns under spin-up(and spin-down) represent. I hope I have provided enough information about my problem and am waiting for someone to address these issues. Have a nice day..!!

[Umberto Martinez]

Hello, HOMO and LUMO correspond to the first state below and above the Fermi level, respectively.
The third column in the molecular energy spectrum correspond to the occupation of the corresponding state, 1 if the state is occupied and 0 if not.

[karn]

Hi, Umberto Martinez for replying. I don't think I have wholly got answers to my questions from previous post. I have 3 questions specifically:
(1) What do first and second column represent? Little elaboration will go a long way in helping me and others.
(2)  As opposed to what you mentioned in your last post, the third column also contains some numbers like 9.999985e-01,8.939647e-02,1.532619e-04 and so on. Should I treat them as zero or what? 
(3) Can you exactly point out HOMO and LUMO for spin-up and spin-down electrons from the result(mpsh0.nc) I attached in my last post? This would do a world of good to me.

Hoping to hear from you soon. Have a great day..!!

[karn]

Would anyone please answer this? I badly need someone's help on this. Thanks in advance.

[Umberto Martinez]

1. First column report the number of the eigenstate.
This number corresponds also to the quantum number to use in the Eigenstate analysis as described here:
http://quantumwise.com/documents/tutorials/latest/MolecularDevice/index.html/chap.analysis.html#sect1.analysis.mpsh
Second column reports the energy of the corresponding eigenstate, in units of eV.

2. fractional occupancy is due to the fact that your system (projected eigenstates) is not a semiconductor or insulator, i.e. no band gap.
Your eigenstates around the Fermi level are very close in energy and due to the Fermi temperature you will find have partial occupancy (Fermi distribution).
You can indeed plot it by plotting column 3 vs column 2 (or 1) .

3. Hard to define HOMO and LUMO for a metallic system.
Formally, for your system they are 279 and 280 and 284 and 285, for spin up and spin down respectively.

You may want to investigate more eigenstate around the Fermi level or change projection.
I hope I have now answered more clearly.
Please, go through the tutorial above and everything should be clear to you.