Nuclear Neutron Scattering Length

In order to calculate nuclear neutron intensities properly, mcdiff has to be provided with the neutron scattering length in units of $10^{-14}$ m.

#-------------------------------------------------------
# Neutron Scattering Length (10^-12 cm) (can be complex)
#-------------------------------------------------------
SCATTERINGLENGTHREAL=0.769
SCATTERINGLENGTHIMAG=0
#  ... note: - if an occupancy other than 1.0 is needed, just reduce 
#              the scattering length linear accordingly