AI 中文总结
研究β′-Mn₃(PO₄)₂高压结构行为，结合同步辐射X射线衍射与密度泛函理论计算。揭示其常压下结构特征，及高压下衍射峰变化、微观结构演变等，表明其高压响应受多种因素影响，为磷酸盐框架压力诱导结构降解提供新认识。
AI 中文摘要
采用同步辐射X射线衍射至20 GPa并结合密度泛函理论计算，研究了β′-Mn₃(PO₄)₂的高压结构行为。常压下，β′-Mn₃(PO₄)₂为单斜结构，具有强各向异性压缩。用三阶Birch-Murnaghan状态方程描述晶胞体积的压力依赖性并确定压缩主轴。14.1 GPa以上，衍射峰显著变宽变弱，归因于与长程晶体学有序丧失相关的不可逆压力诱导结构无序。解压后无序态仍存在，证明转变不可逆。计算准确再现实验压缩行为并揭示微观结构演变。压缩主要通过Mn-O多面体畸变实现，PO₄四面体较刚性。一些初始五配位Mn位点在压缩下逐渐向八面体配位演变，部分MnO₆多面体在无序开始前出现异常畸变和弹性软化。弹性常数计算表明晶体相在实验观察到的转变压力附近变得机械不稳定。实验和计算结果表明β′-Mn₃(PO₄)₂的高压响应受框架复杂性、各向异性多面体压缩性和弹性不稳定性相互作用影响，为结构复杂的磷酸盐框架中压力诱导的结构降解提供新见解。
英文摘要
The high-pressure structural behavior of $β^\prime$-Mn$_3$(PO$_4$)$_2$ was investigated using synchrotron X-ray diffraction up to 20 GPa combined with density-functional theory calculations. At ambient conditions, $β^\prime$-Mn$_3$(PO$_4$)$_2$ crystallizes in a monoclinic structure that exhibits strongly anisotropic compression. The pressure dependence of the unit-cell volume was described using a third-order Birch--Murnaghan equation of state, and the principal axes of compressibility were determined. Above 14.1 GPa, significant broadening and weakening of the diffraction peaks are attributed to the onset of irreversible pressure-induced structural disorder associated with the loss of long-range crystallographic order. The disordered state persists after decompression to ambient pressure, demonstrating the irreversible nature of the transformation. The calculations accurately reproduce the experimental compressional behavior and provide insights into the microscopic structural evolution under pressure. Compression is mainly accommodated through distortions of the Mn--O polyhedra, whereas the PO$_4$ tetrahedra behave as comparatively rigid units. Several initially penta-coordinated Mn sites progressively evolve toward octahedral coordination under compression, while selected MnO$_6$ polyhedra exhibit anomalous distortions and elastic softening preceding the onset of disorder. Elastic constant calculations further reveal that the crystalline phase becomes mechanically unstable near the experimentally observed transition pressure. The combined experimental and computational results suggest that the HP response of $β^\prime$-Mn$_3$(PO$_4$)$_2$ is influenced by the interplay between framework complexity, anisotropic polyhedral compressibility, and elastic instability, providing new insight into pressure-induced structural degradation in structurally complex phosphate frameworks.
Comments33 pages, 9 figures, 3 tables
Journal refDalton Transactions (2026)
DOI：10.1039/d6dt01297c 10.1039/d6dt01297c 10.1039/d6dt01297c
