一种新颖的固态钐硒化物Sm_8eS_(10)的结构研究

Structural Investigation of a Novel Solid-State Samarium Selenide, Sm_8Se_(10)

标题化合物系采用固相法合成得到,化学式为Sm_8Se_(10),四方晶系,I4_1/a空间群,晶胞参数:a=1.2000(7),c=1.4075(30)nm,V=2.027(5)nm^3,F(000)=3344,Z=4,D_c=6.53g/cm^3.结构精修收敛后一致性因子R=0.071,R_w=0.067.化合物中稀土钐的配位多面体系由畸变三方柱演化而来,八个Sm原子构成类S_4N_4的笼状八元环,这些八元环沿晶轴c方向呈现出规整的排列结构.结构数据分析和电阻率测量表明Sm_8Se_(10)具有价态涨落现象,是一个混合价化合物.

The title compound (k-phase) was prepared by solid state reaction and chemical transport reaction. Formula: Sm_8Se_(10), tetragonal, I4_1/α, α= 1.2000(7), c = 1.4075(30) nm, V= 2.027(5)nm^3, F (000) =3344, Z=4, D_c= 6.53g/cm^3, R= 0.071, R_w= 0.067. The coordination polyhedra around the Sm atoms are derived from distorted triangular prisms. A cage eight-member ring formed by eight Sm atoms is similar to that of S_4N_4. The projection of these Sm_8 rings along the c direction exhibits a very regular array. Structural parameter analysis and electrical resistivity measurements indicate that Sm_8Se_(10) is a mixed-valence rare earth compound.