  The local atomic order of an amorphous Ga$_{50}$Se$_{50}$ alloy produced by
Mechanical Alloying (MA) was studied by the Extended X-ray Absorption Fine
Structure (EXAFS) and X-ray Diffraction (XRD) techniques and by Reverse Monte
Carlo (RMC) simulations of its total x-ray structure factor. The coordination
numbers and interatomic distances for the first neighbors were determined by
means of EXAFS analysis and RMC simulations. The RMC simulations also furnished
the partial pair distribution functions $G^{\text{RMC}}_{\text{Ga-Ga}}(r)$,
$G^{\text{RMC}}_{\text{Ga-Se}}(r)$ and $G^{\text{RMC}}_{\text{Se-Se}}(r)$. The
results obtained indicated that there are important differences among the local
structure of the amorphous Ga$_{50}$Se$_{50}$ alloy produced by MA and those of
the corresponding crystals, since there are Se-Se pairs in the first
coordination shell of the amorphous alloy that are forbidden in the
Ga$_{50}$Se$_{50}$ crystals.
