Poddig Hagen, Doert Thomas
Faculty of Chemistry and Food Chemistry, Technische Universität Dresden, Bergstraße 66, Dresden, 01069, Germany.
Acta Crystallogr B Struct Sci Cryst Eng Mater. 2020 Dec 1;76(Pt 6):1092-1099. doi: 10.1107/S2052520620013797. Epub 2020 Nov 17.
The two-dimensionally incommensurately modulated crystal structures of the compounds RETe (RE = La, Pr, Nd) were investigated by single-crystal X-ray diffraction. The compounds crystallize in the tetragonal superspace group P4/n(αβ½)00(-βα½)00 (No. 85.2.58.2) with q = αa*+βb*+½c* and q = -βa*+αb*+½c* and share a common motif of an alternating stacking of a puckered [RETe] layer and a planar [Te] layer. This basic structural motif is observed for all reported compounds with unusually large anisotropic displacement parameters in the planar [Te] layer. Taking the modulation into account, a distortion from this perfect square planar net is noted along with vacancies in the planar [Te] layer. The distortion leads to the formation of different discrete anions, like Te, Te and Te, similar to previously reported structures for REX compounds (RE = trivalent rare earth metal, X = S, Se, Te). The Te-Te distances in the modulated [Te] layer are found in a narrow range as compared to those in the corresponding sulfides and selenides.
通过单晶X射线衍射研究了化合物RETe（RE = La、Pr、Nd）的二维非相称调制晶体结构。这些化合物结晶于四方超空间群P4/n(αβ½)00(-βα½)00（编号85.2.58.2），其中q = αa*+βb*+½c且q = -βa+αb*+½c*，并且具有褶皱的[RETe]层和平坦的[Te]层交替堆叠的共同结构单元。在平面[Te]层中具有异常大的各向异性位移参数的所有已报道化合物中都观察到了这种基本结构单元。考虑到调制情况，注意到与该完美正方形平面网络存在畸变，同时平面[Te]层中存在空位。这种畸变导致形成不同的离散阴离子，如Te、Te和Te，类似于先前报道的REX化合物（RE = 三价稀土金属，X = S、Se、Te）的结构。与相应的硫化物和硒化物相比，调制后的[Te]层中的Te - Te距离处于较窄的范围内。
