This twist angle is close to 60 degrees. To 
construct the superlattice, we start with the 
60 degree rotated structure: Bernal stacking.
And then perform a small twist using the hex.table

The input file, twist.inp, here is constructed using i = 9
entry of hex.table (../../hex.table). We add the following lines 
in the input:

layer2_from_file:
True basis_pos_crys_layer2

basis_pos_crys file contains the basis for layer 1. 
basis_pos_crys_layer2 contains the basis for layer 2,
which is chosen to produce the Bernal stacking.
Hence the stacking is Bernal at the origin in the 
superlattice.

To run this example, run from command line:

python path_to_Twister_1.0/src/twister.py

The superlattice vectors in units of celldm1,
and atom positions (in Angstroms) constituting 
the superlattice are provided in superlattice.dat

A reference Quantum Espresso input file, in.QE, for 
this superlattice is also provided.
