Hematolite; a complex dense-packed sheet structure
Hematolite; a complex dense-packed sheet structure
复制标题
赤铁矿；
作者：
P. Moore;T. Araki
赤铁矿，（Mn'z+,Mg,Al）rr(OH.)zg(AsOr)(AsOn)r, Z: 3，菱形体，空间群R3， a = 8.275(5), c = 36.60(5)4，是一种异常复杂的致密堆积氧化物结构。R: 0。l表示l47l个独立反射。该结构基于密集堆积的堆叠序列。它包括34个氧和一个孤电子对，每层有7个阴离子。将孤对作为阴离子计算，一般公式为MruTsQsr，其中M为八面体，I为四面体，@为阴离子居群。亚砷酸盐的三角金字塔在几何上与共体Mr(OH)r(HrO)r(AsOrXAsOn)r的环境相似。五个非等效层是：(1)孤立的八面体；(2)八面体薄片和四面体薄片与锰+锰3+SiOr中发现的薄片相同；(3)与(2)相似的八面体和三角锥体薄片；(4)岛状八面体和四面体；(5)在黄铜矿中发现的lM”6rl型八面体薄片。这些层通过角共享和边缘共享相互耦合。赤铁矿是形成更复杂结构的kraisslite， M1$Zn'(OH),,(AsOo)o(SiOn)，和mcgoite， It bbbb1fi,Zn (OH),,(AsOe)(AsO.),(SiO')g的关键。本文提出了这些结构和二长石Mn?iMnl+(OH)r(AsOs)6（SiOr）的模型。
Hematolite, (Mn'z+,Mg,Al)rr(OH.)zg(AsOr)(AsOn)r, Z : 3, rhombohedral, space group R3, a = 8.275(5), c = 36.60(5)4, is a dense-packed oxide structure of unusual complexity. R : 0.ll for l47l independent reflections. The structure is based on the dense-packed stacking sequence .hhhch. which includes 34 oxygens and one lone electron pair with seven anions per layer. Counting the lone pair as an anion, the general formula is MruTsQsr, where M : octahedral, I = tetrahedral, and @ : anion populations. The arsenite trigonal pyramid is geometrically similar and occurs in an environment similar to that found in synadelphite, Mr(OH)r(HrO)r(AsOrXAsOn)r. The five non-equivalent layers are: (l) isolated octahedra; (2) octahedral and tetrahedral sheet identical to that found in welinite, Mna+Mn3+SiOr; (3) octahedral and trigonal pyramidal sheet much like (2); (4) insular octahedra and tetrahedra, and (5) octahedral sheets of the type lM"6rlfound in chalcophanite. These layers are coupled to each other by corner- and edgesharing. Hematolite is a key to the more complicated structures of kraisslite, M1$Zn'(OH),,(AsOo)o(SiOn),, and mcgovernite, It|1fi,Zn (OH),,(AsOe)(AsO.),(SiO')g. Models are proposed for these structures and for dixenite, Mn?iMnl+(OH)r(AsOs)6(SiOr).