Finding BandGap

[medeepak]

hi

i am new to this forum
can anyone please tell me how to find bandgap/bandstructure of a graphene nanoribbon
i followed the tutorial but bandstructure option is not there in analysis function
also i dont know how to access the eigen values that are computed during the run as band gap can be found from there using homo and lumo values

regards
deepak

[Anders Blom]

If you follow this tutorial for ATK 10.8, you will see how to plot the band structure of a GNR. The band gap can often be found easily by inspection in these 1d systems; more generally, the best way is to compute the density of states however.

[medeepak]

hi
i tried building the same structure through builder but in the density of states plot i dont get any value
what can be the reason
also if i use custom builder i dont get density of states in analysis option

[ugglebot]

Your question is quite confusing Please provide (much) more details, like scripts, plots, etc.

[medeepak]

hi
i have attached the structure i made
when i simulate DOS the plot is empty
kindly find the problem with my structure

[zh]

If you do the band structure calculation, the band gap can be easily found from the band structure plot. Sometime, due to the broadening technique used in the DOS calculation, the band gap found from the DOS plot may look smaller than the one obtained from the band structure plot.

[medeepak]

hi

bandstructure option is not there in analysis menu when i build it this way

[Anders Blom]

I took your file and dropped it on the Scripter in VNL 10.8. If I double-click "Analysis", I can choose "Bandstructure" (although of course first you should have a "New Calculator" there too). Set the relevant parameters as needed, including the NetCDF file, run the calculation, then locate the produced NC file, and select the band structure and click the "Plot" button.

[medeepak]

Hi

i have the new calculator menu while i dont have band structure under analysis
i am using vnl in trial license
is it because of that??
and can you kindly tell me why am i not getting any values in my density of states plot

regards
deepak

[Anders Blom]

No, it's not because of the trial license. I have no idea why you don't see it. Double-click "Analysis" and you see what? A menu will open up, containing a lot of quantities, incl BandStructure.

[medeepak]

Options under my analysis menu in order are

density of states
effective potential
eigenstate
electron density
electron difference density
electrostatic difference potential
external potential
forces
molecular energy spectrum
mulliken population
total energy

Band Structure is not there

[Anders Blom]

This means your system is a molecule, not a periodic structure. Band structure can only be computed for BulkConfigurations.

[medeepak]

so is there any way to find its band gap???

[medeepak]

i noticed this error now only
There are no atoms in my left electrode
even if i increase its width it dooesnt go away

[medeepak]

hi

i wrote a script file for my molecular configuration to find energy bands which requires ATK.KohnSham Method

but when i try to run it through
$ atk <filename>.py
i get the error
atk command not found

i tried vnl <filename>.py
now the software opens but still i dont think it is importing ATK.KohnSham method
it shows the error
ATK.KohnSham module not found

i tried to add the path variable using

export PATH=$PATH:/opt/QuantumWise/atk-10.8.2/vnl/bin

still the same error persists

kindly help