how to get 3D bandstructure ?exactly Dirac cone

[hzkvictory]

ATK calculate bandstructure and plot it along high-symmetry lines.
when I need to plot 3D dirac cones, I am despaired, because i can't do it.
how to extract data from the *.nc and plot the dirac cone of graphene unit ?
attched is the plot i want

[zh]

Actually, what you want do is the calculation of the Fermi surface.  It cannot be done in  an automatic way. You need to a bit coding by extending the procedure of band structures calculations.

[hzkvictory]

would you give some detailed instructions?
actually, i think 3d-bandstructure is beautiful and should be in the galleary.

[zh]

1. generate many k-points in the first Brillouin zone using a very dense k-mesh;
2. calculate the eigenvalues for those k-points generated in the 1st step;
3. arrange the calculated data into a proper format, e.g, bxsf for Fermi surface; and then visualize it by XCRYSDEN .
   or in the following format
    kx_1     ky_1     eigenvalue_1 (highest occupied \pi band)
.....
    kx_n    ky_n    eigenvalue_n (highest occupied \pi band)

    kx_1   ky_1     eigenvalue_1 (lowest unoccupied \pi band)
....
    kx_n    ky_n    eigenvalue_n (lowest unoccupied \pi band)

The data in the above format can by plotted by the GNUPLOT, python matplotlib, or MATLAB.

[hzkvictory]

under your instruction, i plot the dirac cone, attached is my work.
i calculated the eigenvalues by vasp, extract them out and plot in origin.
(i admit the plot is ugly and i am trying to do better )

my addtional question:
how to extract the eigenvalues in *.nc under extended huckel method calculated by atk?
because i really don't see the eigenvalues when i just open the *.nc in Editor of Virtual NanoLab.