DOS and bandstructure of a ZGNR

[Luis M. Villamagua C.]

Can you kindly help me understand my results for bulk zigzag Chirality? Could be that I am not reading the results properly

I analysed the DOS and Band Structure of AGNR, obtaining results quite reasonable. However, when I carried out the same analyses for ZGNR I got results that does not make any sense to me; there are many lines crossing.

I followed this tutorial (http://www.quantumwise.com/documents/tutorials/latest/GrapheneBloch/index.html/chap.bandstructure.html) and I expected to see something close to that.


This is what I did .....

(1) Relaxed a pristine 8ZGNR 12 times repeated

Calculator: DFT
k-point mesh: 1x1x9
Grid mesh cut-off: 75 Hartree
Basis set: DoubleZetaPolazired for both Hydrogen and Carbon

(2) On the border of the 8ZGNR a Stone-Wale defect was inserted

The SW defect was inserted at the middle of the ribbon along the z direction


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(3) Relaxed the nanoribbon with the defect included

I allowed to move the atoms that were at maximum 6AA around the defect.

(4) Calculated the DOS and Band structure

Calculator: DFT
k-point mesh: 1x1x21
Grid mesh cut-off: 75 Hartree
Basis set: DoubleZetaPolazired for both Hydrogen and Carbon

DOS block
k-point grid 1x1x21
Energy Zero: Fermi Level
Bands above the Fermi level: All

BandStructure block
points per segment: 200
Brillioum zone route: G, Z

As I understand, if I insert a defect on the border of a ZigZag Nanoribbon (as specified above), the bandgap should increase. In my case however, this is not happening.

I have no clue about what could the problem be. I attach the graphs of my simulations.


Regards,
Luis