Hybler Jiří, Durovič Slavomil
Institute of Physics, Academy of Sciences of the Czech Republik, v.v.i., Na Slovance 2, CZ-182 21 Praha 8, Czech Republic.
Acta Crystallogr B Struct Sci Cryst Eng Mater. 2013 Dec;69(Pt 6):570-83. doi: 10.1107/S2052519213024238. Epub 2013 Oct 23.
Kermesite, Sb2S2O, is a desymmetrized order-disorder (OD) structure of layers. Two data sets were recorded using twinned crystals from Pezinok, Slovakia (named as Pz21, Pz24). The primitive unit cell is triclinic, P1, Z = 4, cell parameters are a = 8.1416 (3), b = 10.6968 (3), c = 5.7835 (2) Å, α = 102.758 (3), β = 110.657 (3), γ = 101.020 (3)°, R(obs) = 0.0243 (Pz21), and a = 8.1372 (2), b = 10.6969 (2), c = 5.7840 (1) Å, α = 102.787 (2), β = 110.606 (2), γ = 100.983 (2)°, R(obs) = 0.0321 (Pz24). The structure can also be described in the non-standard pseudo-monoclinic octuple (Z = 32), F-centered (Kupčík) cell with extra points in 1/4,1/4,0; 1/4,3/4,1/2; 3/4,1/4,1/2; 3/4,3/4,0, with parameters a = 21.6466 (9), b = 8.1416 (3), c = 20.3824 (9) Å, α = 90.079 (4), β = 101.985 (5), γ = 89.948 (4)° (Pz21), and a = 21.6558 (5), b = 8.1372 (2), c = 20.3859 (8) Å, α = 90.028 (3), β = 101.994 (3), γ = 89.986 (2)° (Pz24). The structure is built of layers parallel to the bc plane, stacked along the a vector of the octuple cell, composed of ribbons parallel to the b vector: (i) ribbon of two strips of SbO5 flattened quadrangular pyramids, sharing apical edges; (ii) ribbon of edge-sharing corrugated lozenges SbO3S. Basal S atoms of pyramids share corners of lozenges. Sb atoms are displaced out of coordination polyhedra into the inter-layer space. The OD layer comprises adjacent halves of the structure building layers. The layer group is A(1)2/m1, the protocell is defined by b, c, (a/4)sin β. The MDO1 (4A) polytype is generated by repetition of the t(1,1/4,0) [or alternatively t(1,-1/4,0)] translation. The co-existence of two kinds of domains give rise to the twinning. The twin operation is 2[010], twin index 2. The total continuation of [. a2 .] generates the MDO2 (2M) polytype, space group A12/a1. Simulated and real diffraction patterns are presented. The important values (edges, angles) and displacements of atoms due to the desymmetrization were evaluated. The comparison with structures of stibnite, bismuthinite and aikinite is added.
硫氧锑矿（Sb₂S₂O）是一种层状的去对称化有序-无序（OD）结构。使用来自斯洛伐克佩日诺克的孪晶记录了两组数据（命名为Pz21、Pz24）。原始晶胞为三斜晶系，P1，Z = 4，晶胞参数为a = 8.1416 (3) Å，b = 10.6968 (3) Å，c = 5.7835 (2) Å，α = 102.758 (3)°，β = 110.657 (3)°，γ = 101.020 (3)°，R(obs) = 0.0243（Pz21），以及a = 8.1372 (2) Å，b = 10.6969 (2) Å，c = 5.7840 (1) Å，α = 102.787 (2)°，β = 110.606 (2)°，γ = 100.983 (2)°，R(obs) = 0.0321（Pz24）。该结构也可以用非标准的伪单斜八倍体（Z = 32）、F心（库普契克）晶胞来描述，在1/4,1/4,0；1/4,3/4,1/2；3/4,1/4,1/2；3/4,3/4,0处有额外的点，参数为a = 21.6466 (9) Å，b = 8.1416 (3) Å，c = 20.3824 (9) Å，α = 90.079 (4)°，β = 101.985 (5)°，γ = 89.948 (4)°（Pz21），以及a = 21.6558 (5) Å，b = 8.1372 (2) Å，c = 20.3859 (8) Å，α = 90.028 (3)°，β = 101.994 (3)°，γ = 89.986 (2)°（Pz24）。该结构由平行于bc平面的层构成，沿着八倍体晶胞的a向量堆叠，由平行于b向量的带组成：（i）由两个扁平四边形金字塔状的SbO₅条带共享顶端边缘组成的带；（ii）由边共享的波纹菱形SbO₃S组成的带。金字塔状的基底S原子共享菱形的角。Sb原子从配位多面体中位移到层间空间。OD层由结构构建层的相邻两半组成。层群为A(1)2/m1，原胞由b、c、(a/4)sin β定义。MDO1（4A）多型体通过t(1,1/4,0) [或者t(1,-1/4,0)]平移的重复产生。两种畴共存导致孪晶。孪晶操作是2[010]，孪晶指数为2。[. a2 .]的完全延续产生MDO2（2M）多型体，空间群为A12/a1。给出了模拟和实际的衍射图样。评估了由于去对称化导致的重要值（边、角）和原子位移。还增加了与辉锑矿、辉铋矿和硫砷银矿结构的比较。
