I agree with Antônio Lucas Rigotti Manesco, k-path in Brillouin zone must be correct because graphene has hexagonal system , the high symmetry point must take the following values

G 0.00 0.00 0.00

M 0.50 0.00 0.00

K -0.333 0.666 0.000

My first guess is that you k-path in Brillouin zone does not represent the high symmetry points you want. I recommend a review on that.

I agree with Antônio Lucas Rigotti Manesco, k-path in Brillouin zone must be correct because graphene has hexagonal system , the high symmetry point must take the following values

G 0.00 0.00 0.00

M 0.50 0.00 0.00

K -0.333 0.666 0.000

I agree with Hamad, I want to suggest you a very useful tool to build your KPOINTS file:

https://www.materialscloud.org/work/tools/seekpath

Hi Movva,

The k-mesh that you use can also have a big effect on the final band structure and 12x12x1 is probably too small. For a metal, it is always important to make sure your k-mesh is dense enough to properly capture the bands crossing at the Fermi energy. From past experience looked at graphene using other codes, I know you can get a small band gap if the k-mesh is not dense enough. To get the proper electronic structure for graphene, I would suggest increasing the size of your k-mesh to something much larger like 41x41x1 or even higher. It is always a good idea to run your calculation with different k-meshes anyway to make sure the calculation is well converged. Best of luck with your calculations!

Thanks for everyone !!

The problem has been solved with the corrected k-path (INCAR attached - hope would help someone)

Note that the Dirac conical intersections move out of the high-symetry points (and a gap can open) under certain kinds of strains.