Institute of Mathematical and Physical Sciences, Aberystwyth University, Aberystwyth SY23 3BZ, UK.
Phys Chem Chem Phys. 2013 Jun 14;15(22):8589-605. doi: 10.1039/c3cp51209f. Epub 2013 Apr 25.
Structural changes in liquids between Al2O3 and Y2O3 are investigated as a function of the composition and during supercooling using high energy X-ray diffraction (HEXRD) techniques combined with containerless aerodynamic levitation. Many-body molecular dynamics simulation techniques utilizing potential models that incorporate anion polarization effects are applied to study the same liquid systems. The X-ray scattering experiments indicate a change in liquid structure during supercooling around a composition 20% Y2O3 (AlY20) that occurs over a narrow temperature interval. We have associated this change in structure with the onset of a liquid-liquid phase transformation. Analysis of the MD simulated structures has allowed the structure changes to be interpreted in terms of Al(3+) and Y(3+) coordination environments and particularly the Y(3+)-Y(3+) structural correlations. We show that the incipient liquid-liquid phase transition behaviour is correlated with local density fluctuations that represent different coordination polyhedra surrounding oxygen ions. The difference in energy and volume associated with this sampling of high and low density basins in the underlying energy landscape is consistent with independent verifications of the volume and enthalpy differences between different amorphous forms. The differences in the high- and low-density configurations match the difference in diffraction patterns observed experimentally.
研究了 Al2O3 和 Y2O3 之间液体的结构变化，作为组成函数和过冷时使用高能 X 射线衍射（HEXRD）技术与无容器空气动力学悬浮相结合。利用包含阴离子极化效应的势模型的多体分子动力学模拟技术应用于研究相同的液体系统。X 射线散射实验表明，在过冷过程中，在组成约 20% Y2O3（AlY20）的液体结构发生变化，这发生在一个狭窄的温度间隔内。我们将这种结构变化与液相-液相相变的开始联系起来。对 MD 模拟结构的分析允许根据 Al(3+)和 Y(3+)配位环境，特别是 Y(3+)-Y(3+)结构相关性来解释结构变化。我们表明，初始液相-液相转变行为与局部密度波动相关，这些波动代表围绕氧离子的不同配位多面体。与不同无定形形式之间的体积和焓差的独立验证一致的是，与在基础能量景观中采样高密度和低密度盆地相关的能量和体积差异。高密度和低密度配置之间的差异与实验观察到的衍射图案的差异相匹配。
