QuantumATK Forum

QuantumATK => General Questions and Answers => Topic started by: Shan on August 18, 2018, 08:21

Title: Different band structure of Graphene for 6 repetitions
Post by: Shan on August 18, 2018, 08:21

Dear Experts,

I was calculating the band structure of graphene by repeating the hexagonal primitive cell for testing purposes.
I repeated the hexagonal primitive cell 2, 3 , 4, 5, 6, 7 and 8 times, respectively.
I have received typical graphene band structure with Dirac point at the 'K' point of brillouin zone for 2, 3, 4, 5, 7, 8 repetition cases.
However, the 6 times repetition case shows a different band structure with Dirac point at 'G' point. (The images are attached below).

Why the band structure is different only for 6 repetitions case ?
Let us say it is a result of folded bands and shrinked brilllouin zone due to the repetition of supercell. Then why we are getting the typical band structure (having dirac point at 'k' point) for 7 and 8 repetition cases ????????????

Please explain.
Awaiting your suggestions.

Title: Re: Different band structure of Graphene for 6 repetitions
Post by: Shan on August 20, 2018, 08:13

Dear Experts and Quantumwise Staff,

May I request you to please take few minutes towards my query please.

Title: Re: Different band structure of Graphene for 6 repetitions
Post by: Petr Khomyakov on August 20, 2018, 15:44

For 3x3, 6x6, 9x9, 12x12 ... = 3n x 3n supercell, where n=1, 2, 3, 4..., the K-point of the primitive hexagonal cell folds on to the G-point. You should check your calculation for the 3x3 supercell.

Title: Re: Different band structure of Graphene for 6 repetitions
Post by: Shan on August 20, 2018, 19:13

Yes Dr. Petr... You are right.
I overlooked the bandstructure for 3*3 repetition.

Thank you so much for the clarification.