Blankenship Trevor V, Wang Xiaoping, Hoffmann Christina, Latturner Susan E
Department of Chemistry and Biochemistry, Florida State University , Tallahassee, Florida 32306, United States.
Inorg Chem. 2014 Oct 6;53(19):10620-6. doi: 10.1021/ic501722d. Epub 2014 Sep 15.
The reaction of arsenic with sources of light elements in a Ca/Li melt leads to the formation of two new arsenide hydride phases. The predominant phase Ca14As6X7 (X = C(4-), N(3-), H(-)) exhibits a new tetragonal structure type in the space group P4/mbm (a = 15.749(1) Å, c = 9.1062(9) Å, Z = 4, R1 = 0.0150). The minor phase LiCa3As2H also has a new structure type in the orthorhombic space group Pnma (a = 11.4064(7) Å, b = 4.2702(3) Å, c = 11.8762(8)Å, Z = 4, R1 = 0.0135). Both phases feature hydride and arsenide anions separated by calcium cations. The red color of these compounds indicates they should be charge-balanced. DOS calculations on LiCa3As2H confirm a band gap of 1.4 eV; UV-vis spectroscopy on Ca14As6X7 shows a band gap of 1.6 eV. Single-crystal neutron diffraction studies were necessary to determine the mixed occupancy of carbon, nitrogen, and hydrogen anions on the six light-element sites in Ca14As6X7; these data indicated an overall stoichiometry of Ca14As6C(0.445)N(1.135)H(4.915).
在钙/锂熔体中，砷与轻元素源发生反应，形成了两个新的砷化氢相。主要相Ca14As6X7（X = C(4-)、N(3-)、H(-)）在空间群P4/mbm中呈现出一种新的四方结构类型（a = 15.749(1) Å，c = 9.1062(9) Å，Z = 4，R1 = 0.0150）。次要相LiCa3As2H在正交空间群Pnma中也具有一种新的结构类型（a = 11.4064(7) Å，b = 4.2702(3) Å，c = 11.8762(8)Å，Z = 4，R1 = 0.0135）。这两个相的特征都是氢化物和砷化物阴离子被钙阳离子隔开。这些化合物的红色表明它们应该是电荷平衡的。对LiCa3As2H的态密度计算证实其带隙为1.4 eV；对Ca14As6X7的紫外-可见光谱显示带隙为1.6 eV。需要进行单晶中子衍射研究来确定Ca14As6X7中六个轻元素位置上碳、氮和氢阴离子的混合占据情况；这些数据表明其总体化学计量比为Ca14As6C(·445)N(1.135)H(4.915)。
