This example show how to create a supercell of diamond-Si
and create a slab based on it

The primitive cell structure is used, stored in POSCAR

To create a convention cell, use the command
pysc.py --task=redefine --sc1=-1,1,1 --sc2=1,-1,1 --sc3=1,1,-1
You can check the generated POSCAR_redefine file 

To create a slab structure, run
pysc.py --task=slab --hkl=111 --thickness=3 --vacuum=20
