Synthesis and crystal structure of Mg2B24C, a new boron-rich boride related to "tetragonal boron I"
Synthesis and crystal structure of Mg2B24C, a new boron-rich boride related to "tetragonal boron I"
复制标题
DOI：
10.1016/j.jssc.2006.04.021
复制
发表时间：
2006-07-01
影响因子：
3.3
通讯作者：
Hillebrecht, Harald
中科院分区：
文献类型：
--
作者：
Adasch, Volker;Hess, Kai-Uwe;Hillebrecht, Harald
在1300 ℃下，用钽安瓿和氮化硼坩埚中的元素反应合成了一种新的富硼硼化镁合金Mg_2B_24C单晶，呈黑色针状和柱状。通过X射线衍射测定晶体结构（P-4 n2，a = 8.9391（13）埃，c = 5.0745（10）埃，Z = 2，713个反射，64个变量，R-1（F）= 0.0235，wR（2）（I）= 0.0591）。它与“四硼γ”密切相关，并且可以被描述为在空隙中具有C和Mg原子的角连接的B-12二十面体的四硼棒堆积。每个B-12二十面体有2个B-C键和10个外面体键连接到其他二十面体，2个在杆内，4 × 2连接到相邻的杆。孤立的C原子是4重配位的，形成扭曲的四面体。Mg被置于三维B12 C网络内的两个晶体学上独立的位置上。Mg 2B 24 C是与具有化学计量组成的“四硼酸T”相关的化合物的第一个实例。(C)2006年爱思唯尔公司All rights reserved.
Single crystals Of Mg2B24C, a new boron-rich boridecarbide of magnesium, were synthesized as black needles and columns by reaction of the elements in Ta ampoules and BN crucibles at 1300 degrees C. The crystal structure was determined by X-ray diffraction (P-4n2, a = 8.9391(13)angstrom, c = 5.0745(10)angstrom, Z = 2, 713 reflections, 64 variables, R-1(F) = 0.0235, wR(2)(I) = 0.0591). It is closely related to "tetragonal boron Gamma' and can be described as a tetragonal rod packing of corner-linked B-12 icosahedra with C and Mg atoms in the voids. Each B-12 icosahedron has 2 B-C bonds and 10 exohedral bonds to other icosabedra, 2 within the rod and 4 x 2 to neighbouring rods. The isolated C atoms are 4-fold coordinated forming distorted tetrahedra. Mg is placed on two crystal] ographically independent positions within the three-dimensional B12C network. Mg2B24C is the first example for a compound related to "tetragonal boron T' with a stoichiometric composition. (C) 2006 Elsevier Inc. All rights reserved.