stal axes: (cart. coord. in units of alat)
-0.5 0.0 0.5
0.0 0.5 0.5
-0.5 0.5 0.0
reciprocal axes: (cart. coord. in units 2 pi/alat)
-1.0 -1.0 1.0
1.0 1.0 1.0
-1.0 1.0 -1.0