The b1 structure is the rock salt structure. 
It has a fcc Bravais lattice and two atoms per cell. When one atom
is in the origin, the other is in the center of the cubic
cell (1/2,1/2,1/2) in units of alat.

The reference directory contains the following files:

asy_tmp.asy :  An asymptote script to plot the Brillouin zone

output_bands.ps : plot of the band structure

output_keconv.ps: plot of the convergence of the total energy with the
                kinetic energy cut-off.

output_mur.ps : a plot of the Murnaghan equation.

sic.elastic.out : the output of the elastic constant calculation.
                  See the end of the file for the elastic constant values.

nacl_ph.exp : experimental inelastic neutron scattering data.

nacl_anhar.exp : experimental thermal expansion.


