  An amorphous Se$_{0.80}$S$_{0.20}$ alloy produced by Mechanical Alloying was
studied by Raman spectroscopy, x-ray diffraction, extended x-ray absorption
fine structure (EXAFS) and optical absorption spectroscopy, and also through
reverse Monte Carlo simulations of its total structure factor and EXAFS data.
Its vibrational modes, optical gap and structural properties as average
interatomic distances and average coordination numbers were determined and
compared to those found for an amorphous Se$_{0.90}$S$_{0.10}$ alloy. The
results indicate that coordination numbers, interatomic distances and also the
gap energy depend on the sulphur concentration.
