Sets of self-consistent oxygen-rare earth (RE = La, Y, Lu, Sc) interatomic potential parameters are derived using a force-matching procedure and utilized in molecular dynamics (MD) simulations for exploring the structures of RE2O3–Al2O3–SiO2 glasses that feature a fixed molar ratio nAl/nSi = 1 but variable RE contents. The structures of RE aluminosilicate (AS) glasses depend markedly on the RE3+ cation field strength (CFS) over both short and intermediate length-scales. We explore these dependencies for glasses incorporating the cations La3+, Y3+, Lu3+ and Sc3+, whose CFSs increase due to the concomitant shrinkage of the ionic radii: RLa > RY > RLu > RSc. This trend is mirrored in decreasing average RE3+ coordination numbers (RE) from La = 6.4 to Sc = 5.4 in the MD-derived data. However, overall the effects from RE3+ CFS elevations on the local glass structures are most pronounced in the O and {Al[4], Al[5], Al[6]} speciations. The former display minor but growing populations of O[0] (“free oxygen ion”) and O[3] (“oxygen tricluster”) moieties. The abundance of AlO5 polyhedra increases significantly from ≈10% in La-based glasses to ≈30% in their Sc counterparts at the expense of the overall dominating AlO4 tetrahedra, whereas the amounts of AlO6 groups remain <5% throughout. We also discuss the Si[4]/Al[p] (p = 4, 5, 6) intermixing and the nature of their oxygen bridges, where the degree of edge-sharing increases together with the RE3+ CFS.
This article is Open Access
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