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
 
to obtain the kpts points we used [[http://sourceforge.net/projects/xeo/|xeo]], that implements the Monkhorst-Pack method to generate a k-points

{{:xeo-menu-kpts.png|}}

{{:si-bulk:kpts-xeo.png|}}

And we obtain :

{{:si-bulk:kpts.png|}}