[QE-users] Linear Dispersion Behavior of Graphene Supercells: Seeking Explanations and Solutions

[David Yao ANSI]

Dear All, 

In studying quantum capacitance of doped graphene, I recently made band structure calculations on pristine graphene using supercells of varying sizes. However, I encountered an unexpected result when increasing the supercell size from 2x2x1 to 4x4x1: the linear dispersion behavior around the K - high symmetry point gradually disappeared. This came as a surprise to me since previous articles I read reported a linear dispersion around the K point for similar supercell sizes. I did some also with a gamma Brillouin zone sampling during scf but had same results. 

What are possible reasons behind this and potential approaches to achieve the desired linear behavior in supercell calculations? 
Are there specific techniques or considerations that need to be taken into account when working with larger supercells of graphene? 

Thank you in advance for your assistance and expertise. 

Regards, 
David Ansi 
Master's student 
University of Sci. and Tech.(KNUST), Ghana 


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