Transformation pathways and isothermal compressibility of a MTN-type clathrasil using penetrating and non-penetrating fluids
Transformation pathways and isothermal compressibility of a MTN-type clathrasil using penetrating and non-penetrating fluids
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DOI：
10.1016/j.micromeso.2018.06.033
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发表时间：
2019-01
影响因子：
5.2
通讯作者：
K. Scheidl;H. Effenberger;T. Yagi;Koichi Momma;R. Miletich
中科院分区：
文献类型：
--
作者：
K. Scheidl;H. Effenberger;T. Yagi;Koichi Momma;R. Miletich
利用原位x射线单晶衍射和拉曼光谱研究了天然mtn型赤白石在高达10.3 GPa的静水压力下的高压行为。实验在金刚石-砧细胞中进行，采用1:1甲醇-乙醇混合物（ME）、氦（He）和氖（Ne）作为传压介质。在非渗透性ME流体中，室温多晶体的单位胞体体积与压力有关，其等温体积模量kt0 = 25.75 (19) GPa。由于Ne和He原子渗透到骨架的笼中，晶体结构明显硬化，导致K T0= 42.5 (1.2) GPa （Ne）和K T0= 58 (2) GPa （He）。在压力的影响下，拉曼光谱的演变和细胞指标的变化表明晶格的扭曲，而不会导致完全的压力诱导非晶化，这在许多类似的多孔结构中观察到。赤白石立方fd_3¯m骨架在非穿透性ME中压缩后，在1.7 ~ 2.2 GPa压力范围内发生第一次转变，在3.9 ~ 4.3 GPa压力范围内发生第二次转变。伴随形成的晶体域不能可靠地确定扭曲的晶体结构。单位胞参数可能表明压力>为1.7 GPa时为单斜度规，压力>为3.9 GPa时为单斜度规或四方度规。然而，在一些样品中，甚至证明了不同晶格畸变程度的晶体域共存。
The high-pressure behavior of the natural MTN-type clathrasil chibaite was investigated with in situ single-crystal X-ray diffraction and Raman spectroscopy under hydrostatic pressures up to 10.3 GPa. The experiments were conducted in diamond-anvil cells using 4: 1 methanol-ethanol mixture (ME), helium (He) and neon (Ne) as pressure-transmitting media. The pressure dependent unit-cell volumes of the room-pressure polymorph yield an isothermal bulk modulus K T0= 25.75 (19) GPa for the compression in the non-penetrating ME fluid. Due to the penetration of the Ne and He atoms into the cages of the framework, the crystal structure is significantly stiffened resulting in K T0= 42.5 (1.2) GPa (Ne) and K T0= 58 (2) GPa (He). Under the influence of pressure both the evolution of the Raman spectra and the change in cell metrics indicate a distortion of the lattice without leading to a complete pressure-induced amorphization, as observed for many comparable porous structures. Compressed in the non-penetrating ME, the cubic F d 3¯ m framework of chibaite undergoes a first transformation step in the pressure range between 1.7 GPa and 2.2 GPa and a second one between 3.9 GPa and 4.3 GPa. The accompanied formation of crystal domains did not allow a reliable determination of the distorted crystal structures. The unit-cell parameters might suggest a monoclinic metric for pressures> 1.7 GPa and a monoclinic or tetragonal metric for pressures> 3.9 GPa. However, in some samples even the co-existence of crystal domains of a different degree of lattice distortions has been proved.