Department of Chemistry, McMaster University, Hamilton, Ontario L8S 4M1, Canada.
Dalton Trans. 2011 Apr 28;40(16):4275-83. doi: 10.1039/c0dt01821j. Epub 2011 Mar 9.
Ternary Gd(5-x)Zr(x)Si(4) silicides were synthesized by arc melting of the constituent elements and subsequent heat treatments. The Gd(5-x)Zr(x)Si(4) phases adopt the orthorhombic Gd(5)Si(4)-type (space group Pnma) structure for x≤ 0.25 and the tetragonal Zr(5)Si(4)-type (space group P4(1)2(1)2) structure for x≥ 1.0, respectively. The samples with intermediate compositions contain two phases. Single-crystal X-ray diffraction reveals a preferential site occupancy for Zr on the three metal sites in the order of M3 > M2 > M1. Size arguments based on the local coordination environments suggest that the larger Gd atoms preferentially occupy the larger M1 site, while the smaller Zr atoms tend to occupy the smaller metal sites, M2 and M3. Tight-binding linear-muffin-tin orbital calculations illustrate a role of the metal-silicon bonds in the metal site occupation. An increase in the valence electron concentration through the Zr substitution weakens the Si-Si interactions but enhances the metal-silicon and metal-metal interactions. The Curie temperature of Gd(5-x)Zr(x)Si(4) decreases gradually with the increasing Zr content.
三元 Gd(5-x)Zr(x)Si(4)硅化物通过电弧熔炼元素和随后的热处理合成。Gd(5-x)Zr(x)Si(4)相分别采用正交的 Gd(5)Si(4)-型（空间群 Pnma）结构（x≤0.25）和四方的 Zr(5)Si(4)-型（空间群 P4(1)2(1)2）结构（x≥1.0）。中间组成的样品包含两相。单晶 X 射线衍射揭示了 Zr 在三个金属位上的优先占据顺序为 M3>M2>M1。基于局部配位环境的大小参数表明，较大的 Gd 原子优先占据较大的 M1 位，而较小的 Zr 原子倾向于占据较小的金属位 M2 和 M3。紧束缚线性 muffin-tin 轨道计算说明了金属-硅键在金属位占据中的作用。通过 Zr 取代增加价电子浓度会削弱 Si-Si 相互作用，但增强金属-硅和金属-金属相互作用。Gd(5-x)Zr(x)Si(4)的居里温度随着 Zr 含量的增加而逐渐降低。
