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In this section, we explain how to choice of the k-point mesh of Si bulk diamond structure. The diamond structure is characterized by two distinct atom per unit cell with relative coordinates (0 ,0 ,0) and (1/4, 1/4, 1/4). The lattice vector is defined in the relative coordinates alat*(1/4, 1/4, 1/4). Detail description of the diamond structure can be found elsewhere. There is an elegant way to rescale atomic coordinates, lattice vector and k-points by only one parameter rescal defined in the section &OPTIONS. Our input atomic coordinates written in Si.bas look like:
2 14 0.00000 0.00000 0.00000 14 0.25000 0.25000 0.25000
the lattice vector is defined in Si.lvs file:
0.50000 0.00000 0.50000 0.00000 0.50000 0.50000 0.50000 0.50000 0.00000
and we use Oh symmetry group to generate a k-points set (file Si.kpts) to obtain the kpts points we used http://sourceforge.net/projects/xeo/:xeo, that implements the Monkhorst-Pack method to generate a k-points
