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Structural and Lattice-Dynamical Properties of Tb2O3 under Compression: A Comparative Study with Rare Earth and Related Sesquioxides.
Inorganic Chemistry ( IF 4.3 ) Pub Date : 2020-06-25 , DOI: 10.1021/acs.inorgchem.0c00834 Jordi Ibáñez 1 , Juan Ángel Sans 2 , Vanesa Cuenca-Gotor 2 , Robert Oliva 3 , Óscar Gomis 4 , Plácida Rodríguez-Hernández 5 , Alfonso Muñoz 5 , Ulises Rodríguez-Mendoza 5 , Matías Velázquez 6 , Philippe Veber 7 , Catalin Popescu 8 , Francisco Javier Manjón 2
Inorganic Chemistry ( IF 4.3 ) Pub Date : 2020-06-25 , DOI: 10.1021/acs.inorgchem.0c00834 Jordi Ibáñez 1 , Juan Ángel Sans 2 , Vanesa Cuenca-Gotor 2 , Robert Oliva 3 , Óscar Gomis 4 , Plácida Rodríguez-Hernández 5 , Alfonso Muñoz 5 , Ulises Rodríguez-Mendoza 5 , Matías Velázquez 6 , Philippe Veber 7 , Catalin Popescu 8 , Francisco Javier Manjón 2
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We report a joint experimental and theoretical investigation of the high pressure structural and vibrational properties of terbium sesquioxide (Tb2O3). Powder X-ray diffraction and Raman scattering measurements show that cubic Ia3̅ (C-type) Tb2O3 undergoes two phase transitions up to 25 GPa. We observe a first irreversible reconstructive transition to the monoclinic C2/m (B-type) phase at ∼7 GPa and a subsequent reversible displacive transition from the monoclinic to the trigonal P3̅m1 (A-type) phase at ∼12 GPa. Thus, Tb2O3 is found to follow the well-known C → B → A phase transition sequence found in other cubic rare earth sesquioxides with cations of larger atomic mass than Tb. Our ab initio theoretical calculations predict phase transition pressures and bulk moduli for the three phases in rather good agreement with experimental results. Moreover, Raman-active modes of the three phases have been monitored as a function of pressure, while lattice-dynamics calculations have allowed us to confirm the assignment of the experimental phonon modes in the C- and A-type phases as well as to make a tentative assignment of the symmetry of most vibrational modes in the B-type phase. Finally, we extract the bulk moduli and the Raman-active mode frequencies together with their pressure coefficients for the three phases of Tb2O3. These results are thoroughly compared and discussed in relation to those reported for rare earth and other related sesquioxides as well as with new calculations for selected sesquioxides. It is concluded that the evolution of the volume and bulk modulus of all the three phases of these technologically relevant compounds exhibit a nearly linear trend with respect to the third power of the ionic radii of the cations and that the values of the bulk moduli for the three phases depend on the filling of the f orbitals.
中文翻译：
压缩状态下Tb2O3的结构和晶格动力学性质：与稀土及相关倍半氧化物的比较研究。
我们报告联合实验和理论研究的三氧化二ter（Tb 2 O 3）的高压结构和振动特性。粉末X射线衍射和拉曼散射测量结果表明，立方IA 3（C型）的铽2 ö 3所经历两种相变至多为25GPa。我们在〜7 GPa处观察到第一个不可逆的向单斜C 2 / m（B型）相的重构转变，随后在〜1 2下从单斜向P 3 P m 1（A型）三角形的可逆位移转变。GPa。因此，Tb 2 O 3被发现遵循众所周知的C→B→的相变序列，该相变序列是在其他立方稀土倍半氧化物中发现的，其阳离子的原子质量大于Tb。我们的从头算理论计算预测了三相的相变压力和整体模量，与实验结果相当吻合。此外，已经监测了三个相的拉曼活性模式作为压力的函数，而晶格动力学计算使我们能够确认在C型和A型相中实验声子模式的分配以及B型相位中大多数振动模式的对称性的初步分配。最后，我们提取了Tb 2三相的体模频率和拉曼有源模式频率以及它们的压力系数O 3。将这些结果与稀土和其他相关倍半氧化物的报道进行了全面比较和讨论，并对选定的倍半氧化物进行了新的计算。结论是，相对于阳离子的离子半径的三次方，这些技术上相关的化合物的所有三相的体积和体积模量的演变表现出近乎线性的趋势，并且该化合物的体积模量值三个阶段取决于f轨道的填充。
更新日期：2020-07-20
中文翻译：
压缩状态下Tb2O3的结构和晶格动力学性质：与稀土及相关倍半氧化物的比较研究。
我们报告联合实验和理论研究的三氧化二ter（Tb 2 O 3）的高压结构和振动特性。粉末X射线衍射和拉曼散射测量结果表明，立方IA 3（C型）的铽2 ö 3所经历两种相变至多为25GPa。我们在〜7 GPa处观察到第一个不可逆的向单斜C 2 / m（B型）相的重构转变，随后在〜1 2下从单斜向P 3 P m 1（A型）三角形的可逆位移转变。GPa。因此，Tb 2 O 3被发现遵循众所周知的C→B→的相变序列，该相变序列是在其他立方稀土倍半氧化物中发现的，其阳离子的原子质量大于Tb。我们的从头算理论计算预测了三相的相变压力和整体模量，与实验结果相当吻合。此外，已经监测了三个相的拉曼活性模式作为压力的函数，而晶格动力学计算使我们能够确认在C型和A型相中实验声子模式的分配以及B型相位中大多数振动模式的对称性的初步分配。最后，我们提取了Tb 2三相的体模频率和拉曼有源模式频率以及它们的压力系数O 3。将这些结果与稀土和其他相关倍半氧化物的报道进行了全面比较和讨论，并对选定的倍半氧化物进行了新的计算。结论是，相对于阳离子的离子半径的三次方，这些技术上相关的化合物的所有三相的体积和体积模量的演变表现出近乎线性的趋势，并且该化合物的体积模量值三个阶段取决于f轨道的填充。
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