发表机构
GFZ Helmholtz Centre for Geosciences; University of Potsdam; Goethe-Universität Frankfurt（GFZ 赫尔姆霍茨地学研究中心; 波茨坦大学; 法兰克福歌德大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究通过高压折射率测量与DFT计算，揭示了NaCl、KCl、CaO、SrO和MgO中阴离子极化率对配位数和键长的依赖，确立了可分离预测因子，并发现O²⁻极化率可转移而Cl⁻不可转移。
AI 中文摘要
几种碱金属氯化物和碱土金属氧化物在环境条件下采用B1结构，并在压缩下转变为B2结构，从而可以在化学性质不同的宿主中独立改变配位数和阳离子-阴离子距离。高压下阴离子极化率的变化主导了这些典型离子固体的光学响应，但其对局部结构和阳离子化学的依赖性在高压下仍缺乏实验约束。在此，我们报告了NaCl、KCl、CaO和SrO在约100、约100、约120和约60 GPa下的折射率，每种物质均处于B1和B2两种结构，并辅以已发表的MgO-B1在140 GPa下的折射率数据和DFT计算。Lorentz-Lorenz分析得出与压力无关的应变极化率参数Λ，范围从KCl-B1的0.34±0.05到MgO-B2的1.57±0.02。我们的结果确立了配位数和阳离子-阴离子距离作为B1和B2结构中阴离子极化率的可分离预测因子。在固定阳离子-阴离子距离下，将阴离子配位数从六增加到八，会使Cl⁻和O²⁻的极化率分别降低约0.34-0.40 ų和约0.38-0.47 ų。我们的结果表明，在固定阳离子-阴离子距离下，O²⁻的极化率在MgO-B1和CaO-B1之间可转移，误差在约0.06 ų以内，并且这种可转移性可能扩展到SrO-B1和B2氧化物。相比之下，Cl⁻的极化率在NaCl-B2和KCl-B2之间不可转移：两者之间的差异随阳离子-阴离子距离变化，从2.65 Å处的约0.2 ų到约2.5 Å处的0。结果表明，B1-B2转变中应变极化率参数的变化分别由O²⁻和Cl⁻极化率对致密化敏感性的降低和增加所控制。
英文摘要
Several alkali chlorides and alkaline-earth oxides adopt the B1 structure at ambient conditions and transform to B2 under compression, allowing to change coordination number and cation-anion distance independently across chemically distinct hosts. The change in anion polarizability under high pressure dominates the optical response of these prototypical ionic solids, yet its dependence on local structure and cation chemistry remains experimentally unconstrained at high pressure. Here we report refractive indices of NaCl, KCl, CaO, and SrO to ~100, ~100, ~120, and ~60 GPa, each in both the B1 and B2 structures, complemented by published MgO-B1 indices to 140 GPa and DFT calculations. Lorentz-Lorenz analysis yields pressure-independent strain polarizability parameters $Λ$ ranging from 0.34$\pm$0.05 for KCl-B1 to 1.57$\pm$0.02 for MgO-B2. Our results establish coordination number and cation-anion distance as separable predictors of anion polarizability in both B1 and B2 structures. Increasing anion coordination from six to eight at fixed cation-anion distance lowers the polarizability of both $Cl^{-}$ and $O^{2-}$ by ~0.34-0.40 $\mathring{A}^3$ and ~0.38-0.47 $\mathring{A}^3$ respectively. Our results suggest that the polarizability of $O^{2-}$ is transferable to within ~0.06 $\mathring{A}^3$ between MgO-B1 and CaO-B1 at fixed cation-anion distance, and that this transferability possibly extends to SrO-B1 and the B2 oxides. In contrast, the polarizability of $Cl^{-}$ is not transferable between NaCl-B2 and KCl-B2: the difference between them varies with cation-anion distance, from ~0.2 $\mathring{A}^3$ at 2.65 $\mathring{A}$ to 0 at ~2.5 $\mathring{A}$. The results show that the change of the strain polarizability parameters across the B1-B2 transition is governed by the decreasing and increasing sensitivities of $O^{2-}$ and $Cl^{-}$ polarizabilities to densification, respectively.
Comments23 pages, 7 figures
