Physical Chemistry Division, Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University, Stockholm, Sweden.
Phys Chem Chem Phys. 2013 Sep 28;15(36):15041-55. doi: 10.1039/c3cp51726h.
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 n(Al)/n(Si) = 1 but variable RE contents. The structures of RE aluminosilicate (AS) glasses depend markedly on the RE(3+) cation field strength (CFS) over both short and intermediate length-scales. We explore these dependencies for glasses incorporating the cations La(3+), Y(3+), Lu(3+) and Sc(3+), whose CFSs increase due to the concomitant shrinkage of the ionic radii: R(La) > R(Y) > R(Lu) > R(Sc). This trend is mirrored in decreasing average RE(3+) coordination numbers (Z(RE)) from Z(La) = 6.4 to Z(Sc) = 5.4 in the MD-derived data. However, overall the effects from RE(3+) 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 RE(3+) CFS.
利用力匹配程序得到了一套自洽的氧-稀土（RE=La、Y、Lu、Sc）原子间相互作用势参数，并将其应用于分子动力学（MD）模拟中，以研究具有固定摩尔比 n（Al）/n（Si）=1 但可变 RE 含量的 RE2O3-Al2O3-SiO2 玻璃的结构。RE 铝硅酸盐（AS）玻璃的结构在短程和中程上都明显依赖于 RE（3+）阳离子场强（CFS）。我们研究了掺入 La（3+）、Y（3+）、Lu（3+）和 Sc（3+）阳离子的玻璃的这些依赖性，这些阳离子的 CFS 随着离子半径的缩小而增大：R（La）>R（Y）>R（Lu）>R（Sc）。这一趋势反映在 MD 推导数据中，RE（3+）平均配位数（Z（RE））从 Z（La）=6.4 降低到 Z（Sc）=5.4。然而，总的来说，RE（3+）CFS 升高对局部玻璃结构的影响在 O 和 {Al([4])，Al([5])，Al([6])} 物种中最为明显。前者显示 O([0])（“游离氧离子”）和 O([3])（“氧三聚体”）部分的含量略有增加，但不断增加。AlO5 多面体的丰度从基于 La 的玻璃中的约 10%显著增加到 Sc 对应物中的约 30%，而 AlO4 四面体的总体主导地位下降，而 AlO6 基团的含量仍保持在整个范围内<5%。我们还讨论了 Si([4])/Al([p])（p=4,5,6）的混合以及它们的氧桥的性质，其中边缘共享的程度随着 RE（3+）CFS 的增加而增加。
