====== BZサンプリング ======

<code>
set_kpts(self, kpts)
set the kpt grid.
 
Parameters:
 
kpts: (n1,n2,n3) or [k1,k2,k3,...] or one of these
chadi-cohen sets:
 
* cc6_1x1
* cc12_2x3
* cc18_sq3xsq3
* cc18_1x1
* cc54_sq3xsq3
* cc54_1x1
* cc162_sq3xsq3
* cc162_1x1
 
(n1,n2,n3) creates an n1 x n2 x n3 monkhorst-pack grid,
[k1,k2,k3,...] creates a kpt-grid based on the kpoints
defined in k1,k2,k3,...
 
There is also a possibility to have Dacapo (fortran) create
the Kpoints in chadi-cohen or monkhorst-pack form. To do this
you need to set the KpointSetup.gridtype attribute, and
KpointSetup.
 
KpointSetup = [3,0,0]
KpointSetup.gridtype = 'ChadiCohen'
 
KpointSetup(1)  Chadi-Cohen k-point set
1       6 k-points 1x1
2       18-kpoints sqrt(3)*sqrt(3)
3       18-kpoints 1x1
4       54-kpoints sqrt(3)*sqrt(3)
5       54-kpoints 1x1
6       162-kpoints 1x1
7       12-kpoints 2x3
8       162-kpoints 3xsqrt 3
 
or
KpointSetup = [4,4,4]
KpointSetup.gridtype = 'MonkhorstPack'
we do not use this functionality.
</code>

<code>
get_ibz_k_points = get_ibz_kpoints(self)
get_ibz_kpoints(self)
return list of kpoints in the irreducible brillouin zone
get_k_point_weights(self)
return the weights on the IBZ kpoints
get_kpts(self)
return the BZ kpts
get_kpts_type(self)
return the kpt grid type
</code>