Weil Matthias
Institute for Chemical Technologies and Analytics, Division of Structural Chemistry, Vienna University of Technology, Getreidemarkt 9/164-SC, A-1060 Vienna, Austria.
Acta Crystallogr Sect E Struct Rep Online. 2013 Apr 24;69(Pt 5):i29. doi: 10.1107/S1600536813010714. Print 2013 May 1.
In the structure of the title compound, magnesium hydroxide hydrogenarsenate (6.75/3/4), two different Mg(2+) ions, one located on a site with symmetry 3m. (occupancy 3/4) and one on a general position, as well as two different AsO3(OH) tetra-hedra (symmetry .m. with partial occupancy for the H atom for one, and symmetry 3m. with full occupancy for the H atom for the other) and one OH(-) ion (site symmetry .m.) are present. Both Mg(2+) ions are octa-hedrally surrounded by O atoms. The MgO6 octa-hedra belonging to the partially occupied Mg(2+) sites share faces, forming chains along [001]. The other type of MgO6 octa-hedra share corners and faces under formation of strands parallel to [001] whereby individual strands are linked through common corner atoms. The two types of AsO3(OH) tetra-hedra inter-link the strands and the chains, building up a three-dimensional framework resembling that of the mineral dumortierite. The OH groups were assigned on basis of bond-valence calculations and crystal chemical considerations.
在标题化合物砷酸氢镁（6.75/3/4）的结构中，存在两种不同的Mg(2+)离子，一种位于对称点3m处（占有率3/4），另一种位于一般位置，同时还存在两种不同的AsO3(OH)四面体（一种的对称点为.m.，H原子部分占有率；另一种的对称点为3m.，H原子完全占有率）以及一个OH(-)离子（点群对称.m.）。两种Mg(2+)离子均被O原子八面体配位。属于部分占据的Mg(2+)位点的MgO6八面体共享面，沿[001]方向形成链。另一种类型的MgO6八面体共享角和面，形成平行于[001]的链束，其中各个链束通过共用角原子相连。两种类型的AsO3(OH)四面体将链束和链相互连接，构建出一个类似于矿物蓝线石的三维框架。OH基团是基于键价计算和晶体化学考虑确定的。
