Structural and thermal investigations of an amorphous GaSe9 alloy using EXAFS, cumulant expansion, and reverse Monte Carlo simulations.

In this article, we investigated structural and thermal properties of an amorphous alloy of the Ga-Se system. The amorphous GaSe9 alloy was produced by mechanical alloying and it was studied using EXAFS spectroscopy and cumulant expansion method. We also made reverse Monte Carlo simulations using the total structure factor S(K) obtained from x-ray diffraction and the EXAFS χ(k) oscillations on Se and Ga K edges as input data. Several parameters, such as average coordination numbers and interatomic distances, structural and thermal disorders, asymmetry of the partial distribution functions gij(r), and Einstein and Debye temperatures, were determined. The gij (E)(r) functions were reconstructed from the cumulants C1, C2, and C3 obtained from the Einstein model, and they were compared to the gij (RMC)(r) functions obtained from the simulations. The simulations also furnished the partial bond angle distribution functions Θijℓ(cosθ), which describe the angular distribution of bonds between first neighbors, and give information about the kind of structural units present in the alloy.

Vibrational, optical and structural studies of an amorphous Se(0.90)S(0.10) alloy produced by mechanical alloying.

The local atomic order of an amorphous Se(0.90)S(0.10) alloy produced by mechanical alloying was studied by x-ray diffraction and extended x-ray absorption fine structure (EXAFS) data obtained at three temperatures, T = 300, 200 and 30 K. From the cumulant analysis of the EXAFS data, structural properties such as average interatomic distances, average coordination numbers, Debye-Waller factors and anharmonicity, given by the third cumulant, were obtained. The results found indicate that there is alloying at an atomic level, and Se-S pairs are more disordered and distorted than Se-Se ones due to the milling process.