1. The problem statement, all variables and given/known data I am running CASTEP DFT software to simulate pristine graphene, and am unsuccessful in obtaining the trademark zero band gap at the k-point as reported in numerous papers to date. Any assistance would be greatly appreciated as the subject is very new but I am keen to push on. It seems likely to me that I probably haven;t got the ground state energy of the system ; how to I go about interrogating this? 2. Relevant equations Software makes use of cell and parameter files. 3. The attempt at a solution I have modified the cell file of graphite available at (http://www.castep.org/Tutorials/BandStructureAndDOS) ; I set the second graphite plane 10 angstroms away so as to reduce the effect on the monolayer being observed. The two atoms have fractional coordinate (0,0,0.25) and (0,0,0.75). Symmetry has been generated, and used point_mp_grid : 9x9x1. band structure point path is G(0,0,0) ; K(1/3,1/3,0) ; M(0,1/2,0) ; G(0,0,0) Parameter file uses PBE method, cut off energy has been set at 500eV, occupancy of atoms is fixed, grid scale is 2.0, no dump cycles and max SCF cycles set as 100. I have mainly tried changing the point sampling (common error). Also tried using basis_precision instead of cut off energy at fine and precise settings. All to no avail thus far. Re: I have uploaded a screenshot capturing the cell and parameter files and the band structure calculation for guidance.