Solute-solvent interactions and atomic cohesion in GeSe4 and GeSe4In5 metallic glasses

The atomic topology and electronic structure of metallic GeSe4 and GeSe4In5 glasses were studied by reverse Monte Carlo (RMC) fitting of x-ray diffraction (XRD), neutron diffraction (ND) and extended x-ray absorption fine structure (EXAFS) datasets and subsequent density functional theory (DFT) of the materials' most representative clusters. The latter were selected on the basis of the distribution of coordination number and density along the radial direction of the RMC simulation box, inclusive of the second coordination shell of inter-atomic interactions. In the case of GeSe4, Ge-centered cluster coordination by matrix elements, was between 14 and 15 while Se centers were principally coordinated by 14. The locus of the highest concentration of 14-fold coordinated clusters was the region up to a radial distance of 4-6 from the RMC simulation box origin; similarly, in the GeSe4In5 alloy, the most representative clusters were located within the radial region of up to 6 from the RMC box origin 14-fold and 15-ordination for all. The introduction of In was found to demote Ge center coordination and number density while In readily contributed its valence population towards saturation of dangling Se bonds, which is in alignment with observations of In intervention towards the disruption of Ge-Se and Se-Se networks. Moreover, In caused the shifting of Ge atomic orbital contributions towards energies markedly lower than those observed in the GeSe4 system. In both the binary and the ternary system, the energy component which was most decisive for cluster stability was owing to molecular orbital interactions.