Rare-Earth Manganese Copper Phosphides REMnCu₄P₃ (RE = Gd–Ho): The First Quaternary Ordered Variants of the YCo₅P₃‑Type Structure

The quaternary rare-earth phosphides REMnCu4P3 (RE = Gd–Ho) were obtained from direct reactions of the elements at 800 °C. They are the first examples in which ordering of two different transition-metal atoms takes place within the orthorhombic YCo5P3-type structure [Pearson symbol oP36, space group Pnma, Z = 4; a = 12.667(2)–12.6489(4) Å, b = 3.8119(7)–3.7755(1) Å, and c = 10.895(2)–10.8632(4) Å for RE = Gd–Ho]. Columns of trigonal prisms centered by P atoms are connected in propellor-shaped units in zigzag arrangements to generate square-pyramidal (CN5) sites that are occupied by Mn atoms and tetrahedral sites (CN4) that are occupied by Cu atoms. Spin-polarized band-structure calculations predict that the hypothetical compound YMnCu4P3 will exhibit magnetic ordering. Electrical resistivity measurements on TbMnCu4P3 indicate a poor metal.四元稀土磷化物REMnCu4P3（其中RE为Gd~Ho）通过单质在800℃下的直接反应制得。该系列化合物是首个在正交晶系YCo5P3型结构[皮尔逊符号（Pearson symbol）oP36，空间群（space group）Pnma，Z=4；当RE为Gd至Ho时，晶胞参数a=12.667(2)~12.6489(4) Å，b=3.8119(7)~3.7755(1) Å，c=10.895(2)~10.8632(4) Å]中实现两种不同过渡金属原子有序排布的体系。以P原子为中心的三角棱柱柱以螺旋桨状单元按锯齿形方式连接，形成由Mn原子占据的四方锥配位（配位数5，CN5）位点，以及由Cu原子占据的四面体配位（配位数4，CN4）位点。自旋极化能带结构计算预测，假想化合物YMnCu4P3将表现出磁有序行为。对TbMnCu4P3的电阻率测试结果表明其呈现弱金属导电特性。