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P21/c Postorthopyroxene γ-LiScGe2O6, a New Dense High-Pressure Polymorph and Its Direct Transformation from the Pbca Structure
Inorganic Chemistry ( IF 4.3 ) Pub Date : 2020-11-27 , DOI: 10.1021/acs.inorgchem.0c02284 Martin Ende 1 , Johannes M. Meusburger 1, 2 , Manuela Zeug 1 , Katharina S. Scheidl 1, 3 , Günther J. Redhammer 4 , Ronald Miletich 1
Inorganic Chemistry ( IF 4.3 ) Pub Date : 2020-11-27 , DOI: 10.1021/acs.inorgchem.0c02284 Martin Ende 1 , Johannes M. Meusburger 1, 2 , Manuela Zeug 1 , Katharina S. Scheidl 1, 3 , Günther J. Redhammer 4 , Ronald Miletich 1
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Orthorhombic β-LiScGe2O6 single crystals were compressed hydrostatically up to 10.35 GPa using a diamond anvil cell and investigated in situ by means of X-ray diffraction and Raman spectroscopy. Crystal-structure investigations at ambient conditions and at high pressure show a structural transition from an orthopyroxene-type Pbca structure (a ≈ 18.43 Å, b ≈ 8.85 Å, and c ≈ 5.34 Å at 8.6 ± 0.1 GPa) to a postorthopyroxene type P21/c structure of the new dense γ-LiScGe2O6 (a ≈ 18.62 Å, b ≈ 8.85 Å, c ≈ 5.20 Å, and β ≈ 93.1° at 9.5 ± 0.1 GPa). The structure refinements reveal displacive shifts of O atoms associated with a rotation of every other tetrahedral-chain unit from the O- to S-type position similar to the postorthopyroxene-type MgSiO3. As a consequence of the oxygen displacement, the coordination number of Li atoms is changing from [5 + 1] to a proper 6-fold coordination. The transition around Pc = 9.0 ± 0.1 GPa is associated with a volume discontinuity of ΔV = −1.6%. This orthopyroxene (OEn-Pbca) to postorthopyroxene (pOEn-P21/c) transition is the second example of this type of transformation. Precise lattice parameters have been determined during isothermal compression. The fit of the unit-cell volumes of β-LiScGe2O6, using a third-order Birch–Murnaghan equation of state, yields V0 = 943.63 ± 0.11 Å3, K0 = 89.8 ± 0.6 GPa, and dK/dP = 4.75 ± 0.18 as parameters. Evaluation of the data points beyond the critical transition pressure using a second-order Birch–Murnaghan equation suggests V0 = 940.6 ± 4.4 Å3 and K0 = 82.4 ± 4.8 GPa. A series of high-pressure Raman spectra confirm the symmetry-related structural transition, with band positions shifting in a noncontinuous manner, thus confirming the proposed first-order transition.
中文翻译：
P 2 1 / ç Postorthopyroxeneγ-LiScGe 2 Ø 6，新密高压变形术及其从直接转化PBCA结构
斜方晶系β-LiScGe 2 ö 6个单晶以使用金刚石砧细胞压缩流体静力高达10.35 GPA和通过X射线衍射和拉曼光谱的装置原位研究。在环境条件下和在高压下结晶结构的调查显示从斜型的结构转变PBCA结构（一个≈18.43埃，b ≈8.85埃，c ^ ≈5.34埃处8.6±0.1 GPa）的一种postorthopyroxene型P 2 1 / ç新密γ-LiScGe的结构2 ö 6（一个≈18.62埃，b ≈8.85埃，Ç ≈5.20埃，β ≈93.1°在9.5±0.1 GPa）的。结构上的改进揭示了O原子的位移，该位移与每隔一个四面体链单元从O型到S型位置的旋转相关，类似于邻位邻苯并茂型MgSiO 3。由于氧置换，Li原子的配位数从[5 +1]变为适当的6倍配位。P c = 9.0±0.1 GPa附近的转变与体积不连续性ΔV = -1.6％有关。该邻苯二酚（OEn- Pbca）转变为后邻苯二酚（pOEn- P 2 1 / c）转换是此类转换的第二个示例。在等温压缩过程中已经确定了精确的晶格参数。的晶胞体积的配合β -LiScGe 2 ö 6，使用状态的三阶桦木-Murnaghan状态方程，产率V 0 = 943.63±0.11埃3，ķ 0 = 89.8±0.6 GPA，和d ķ / d P = 4.75±0.18作为参数。除了使用二阶桦木-Murnaghan状态方程的临界转变压力数据点的评价表明V 0 = 940.6±4.4埃3和ķ 0= 82.4±4.8 GPa。一系列高压拉曼光谱证实了与对称性有关的结构转变，能带位置以非连续方式移动，从而证实了拟议的一阶转变。
更新日期：2020-12-21
中文翻译：
P 2 1 / ç Postorthopyroxeneγ-LiScGe 2 Ø 6，新密高压变形术及其从直接转化PBCA结构
斜方晶系β-LiScGe 2 ö 6个单晶以使用金刚石砧细胞压缩流体静力高达10.35 GPA和通过X射线衍射和拉曼光谱的装置原位研究。在环境条件下和在高压下结晶结构的调查显示从斜型的结构转变PBCA结构（一个≈18.43埃，b ≈8.85埃，c ^ ≈5.34埃处8.6±0.1 GPa）的一种postorthopyroxene型P 2 1 / ç新密γ-LiScGe的结构2 ö 6（一个≈18.62埃，b ≈8.85埃，Ç ≈5.20埃，β ≈93.1°在9.5±0.1 GPa）的。结构上的改进揭示了O原子的位移，该位移与每隔一个四面体链单元从O型到S型位置的旋转相关，类似于邻位邻苯并茂型MgSiO 3。由于氧置换，Li原子的配位数从[5 +1]变为适当的6倍配位。P c = 9.0±0.1 GPa附近的转变与体积不连续性ΔV = -1.6％有关。该邻苯二酚（OEn- Pbca）转变为后邻苯二酚（pOEn- P 2 1 / c）转换是此类转换的第二个示例。在等温压缩过程中已经确定了精确的晶格参数。的晶胞体积的配合β -LiScGe 2 ö 6，使用状态的三阶桦木-Murnaghan状态方程，产率V 0 = 943.63±0.11埃3，ķ 0 = 89.8±0.6 GPA，和d ķ / d P = 4.75±0.18作为参数。除了使用二阶桦木-Murnaghan状态方程的临界转变压力数据点的评价表明V 0 = 940.6±4.4埃3和ķ 0= 82.4±4.8 GPa。一系列高压拉曼光谱证实了与对称性有关的结构转变，能带位置以非连续方式移动，从而证实了拟议的一阶转变。
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