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QuantumATK => General Questions and Answers => Topic started by: karn on March 25, 2015, 06:44

Title: Change in HOMO-LUMO gap with change in Voltage
Post by: karn on March 25, 2015, 06:44

Hi, Everyone

I would be grateful if you could help me resolve an issue i am having. I earlier calculated I-V characteristic of a two probe geometry(specifically a MTJ) through Analysis -> I-V curve method for PC and APC. Now I want to find the HOMO-LUMO gap at different bias voltages. Please tell me how i can find this change in HOMO-LUMO gap with the change in bias voltages from above I-V curve result at the earliest. I look forward to your comments. Have a blessed day..!! :)

Title: Re: Change in HOMO-LUMO gap with change in Voltage
Post by: Umberto Martinez on March 25, 2015, 10:55

Did you save the SCF states at different bias voltages by setting the selfconsistent_configurations_filename parameter?
If yes, you can simply perform a device density of state analysis for each of your finite bias states.
Something like:

Code: python

configurations = nlread('ivcurve_selfconsistent_configurations.nc', DeviceConfiguration)
for device_configuration in configurations:
    device_density_of_states = DeviceDensityOfStates(
              ......

You can also add any other analysis that may help you with your problem. See for example http://quantumwise.com/documents/tutorials/latest/MolecularDevice/index.html/chap.analysis.html

Title: Re: Change in HOMO-LUMO gap with change in Voltage
Post by: karn on March 25, 2015, 14:11

I am not sure if I fully understand what you mean by the first question in your last post. :'( But I  am guessing you mean an .nc file(s) like "ivcurve_selfconsistent_configurations.nc", which I do have and I got it by calculating I-V curve for the MTJ in PC(and later in APC). In order to find HOMO and LUMO, I think I need to calculate Molecular Energy Spectrum for spin up and spin down electrons in PC as well as APC at different bias voltages for the MTJ. So I would be grateful if you could explain in a bit detail as to how to go about this calculation with aforementioned nc file(s) at my disposal. Waiting for your replay at the earliest. You have a nice day..!! :)

Title: Re: Change in HOMO-LUMO gap with change in Voltage
Post by: karn on March 26, 2015, 20:29

Sir, I would really appreciate if you could provide an answer to previous question(s) promptly. I am actually kind of stuck at it and I gotta move on. So just waiting for your expert comments. You have a great day..!!