Ruseikina Anna V, Grigoriev Maxim V, Locke Ralf J C, Chernyshev Vladimir A, Schleid Thomas
Laboratory of Theory and Optimization of Chemical and Technological Processes, University of Tyumen, 625003 Tyumen, Russia.
Institute for Inorganic Chemistry, University of Stuttgart, D-70569 Stuttgart, Germany.
Materials (Basel). 2024 Jul 9;17(14):3378. doi: 10.3390/ma17143378.
The layered orthorhombic quaternary tellurides EuCuTe ( = Ho, Tm, Sc) with symmetry were first synthesized. Single crystals of the compounds up to 500 μm in size were obtained by the halide-flux method at 1120 K from elements taken in a ratio of Eu//Cu/Te = 1:1:1:3. In the series of compounds, the changes in lattice parameters were in the ranges = 4.3129(3)-4.2341(3) Å, = 14.3150(9)-14.1562(9) Å, = 11.2312(7)-10.8698(7) Å, = 693.40(8)-651.52(7) Å. In the structures, the cations Eu, ( = Ho, Tm, Sc), and Cu occupied independent crystallographic positions. The structures were built with distorted copper tetrahedra forming infinite chains [CuTe] and octahedra [Te] forming two-dimensional layers along the axis. These coordination polyhedra formed parallel two-dimensional layers CuRETe32-∞2. Between the layers, along the -axis, chains of europium trigonal prisms [EuTe] were located. Regularities in the variation of structural parameters and the degree of distortion of coordination polyhedra depending on the ionic radius of the rare-earth metal in the compounds EuCu ( = Ho, Er, Tm, Lu, Sc; = S, Se, Te) were established. It is shown that with a decrease in the ionic radius () in the compounds EuCuTe, the unit-cell volume, bond length (-Te), distortion degree [CuTe], and crystallographic compression of layers [CuTe] decreased. The distortion degree of tetrahedral polyhedra [Cu], as well as the structural parameters in europium rare-earth copper tellurides EuCuTe, were higher than in isostructural quaternary chalcogenides. Ab initio calculations of the crystalline structure, phonon spectrum, and elastic properties of compounds EuCuTe ( = Ho, Tm, and Sc) ere conducted. The types and wave numbers of fundamental modes were determined, and the involvement of ions in IR and Raman modes was assessed. The calculated data of the crystal structure correlated well with the experimental results.
首次合成了具有(D_{2h})对称性的层状正交晶系四元碲化物(EuCuTe)（(R = Ho)、(Tm)、(Sc)）。通过卤化物助熔剂法在(1120K)下，以(Eu∶Cu∶Te = 1∶1∶1∶3)的比例从元素合成出尺寸达(500μm)的该化合物单晶。在该系列化合物中，晶格参数的变化范围为：(a = 4.3129(3) - 4.2341(3) Å)，(b = 14.3150(9) - 14.1562(9) Å)，(c = 11.2312(7) - 10.8698(7) Å)，(V = 693.40(8) - 651.52(7) ų)。在这些结构中，阳离子(Eu)、(R)（(R = Ho)、(Tm)、(Sc)）和(Cu)占据独立的晶体学位置。结构由扭曲的铜四面体形成无限链([CuTe])以及八面体([Te])沿着(b)轴形成二维层构建而成。这些配位多面体形成平行的二维层(CuRETe_3^{2 - ∞})。在层之间，沿着(c)轴，存在铕三角棱柱([EuTe])链。确定了化合物(EuCuRTe)（(R = Ho)、(Er)、(Tm)、(Lu)、(Sc)；(X = S)、(Se)、(Te)）中结构参数的变化规律以及配位多面体的畸变程度与稀土金属离子半径的关系。结果表明，在化合物(EuCuTe)中，随着离子半径（(R)）减小，晶胞体积、键长（(Cu - Te)）、畸变程度([CuTe])以及层的晶体学压缩([CuTe])均减小。四面体多面体([Cu])的畸变程度以及铕稀土铜碲化物(EuCuTe)中的结构参数高于同结构四元硫族化合物。对化合物(EuCuTe)（(R = Ho)、(Tm)和(Sc)）的晶体结构、声子谱和弹性性质进行了从头算计算。确定了基本模式的类型和波数，并评估了离子在红外和拉曼模式中的参与情况。晶体结构的计算数据与实验结果良好相关。
