Poupon Morgane, Barrier Nicolas, Petit Sébastien, Boudin Sophie
Laboratoire CRISMAT, UMR 6508 CNRS ENCAEN, 6 bd Maréchal Juin, 14050 CAEN Cedex 4, France.
Dalton Trans. 2017 Feb 14;46(6):1927-1935. doi: 10.1039/c6dt04449b.
A new β-CdTeO polymorph was obtained by hydrothermal synthesis and its structure was solved ab initio from powder X-ray diffraction data. It appears that the structure of β-CdTeO (Pnma, Z = 16, a = 7.45850(3) Å, b = 14.52185(6) Å, c = 11.04584(5) Å) is closely related to that of α-CdTeO (P2/c, Z = 8, a = 7.790(1) Å, b = 11.253(2) Å, c = 7.418(1) Å, β = 113.5(1)°) previously reported. The 3D framework of β-CdTeO is built of both [CdO] distorted octahedra and [CdO] mono-capped trigonal prisms and three different tellurium polyhedra: trigonal pyramids [TeOE] and trigonal bipyramids [TeOE] and [TeOE] (E denotes the lone pair of Te). The electronic structure calculations based on density functional theory methods show that at the ground state α-CdTeO is slightly more stable than β-CdTeO with an energy difference of 4.64 kJ mol. The band structures confirm the results of optical UV-Vis spectroscopy measurements: both polymorphs are wide bandgap semiconductors with E = 3.55 eV for β-CdTeO and E = 3.91 eV for α-CdTeO. The DOS calculations for both polymorphs enable one to understand that the presence of the [TeOE] polyhedra in β-CdTeO (absent in α-CdTeO) lowers its bandgap. Above 540 °C β-CdTeO transforms into α-CdTeO in a first order phase transition.
通过水热合成法获得了一种新型β-CdTeO多晶型物，并根据粉末X射线衍射数据从头算解析了其结构。β-CdTeO（Pnma，Z = 16，a = 7.45850(3) Å，b = 14.52185(6) Å，c = 11.04584(5) Å）的结构似乎与先前报道的α-CdTeO（P2/c，Z = 8，a = 7.790(1) Å，b = 11.253(2) Å，c = 7.418(1) Å，β = 113.5(1)°）密切相关。β-CdTeO的三维骨架由扭曲的[CdO]八面体和[CdO]单帽三角棱柱以及三种不同的碲多面体构成：三角锥[TeOE]、三角双锥[TeOE]和[TeOE]（E表示碲的孤对电子）。基于密度泛函理论方法的电子结构计算表明，在基态下α-CdTeO比β-CdTeO略稳定，能量差为4.64 kJ/mol。能带结构证实了紫外-可见光谱测量的结果：两种多晶型物均为宽带隙半导体，β-CdTeO的E = 3.55 eV，α-CdTeO的E = 3.91 eV。两种多晶型物的态密度计算使人们能够理解，β-CdTeO中[TeOE]多面体（α-CdTeO中不存在）的存在降低了其带隙。在540℃以上，β-CdTeO以一级相变转变为α-CdTeO。
