Steciuk Gwladys, Majzlan Juraj, Plášil Jakub
Department of Structure Analysis, Institute of Physics, Czech Academy of Sciences, Na Slovance 1999/2, Prague 8, 182 21, Czech Republic.
Institute of Geosciences, Friedrich-Schiller University, Burgweg 11, Jena, 07749, Germany.
IUCrJ. 2021 Jan 1;8(Pt 1):116-123. doi: 10.1107/S2052252520015626.
Kaatialaite mineral Fe[AsO(OH)]5HO from Jáchymov, Czech Republic forms white aggregates of needle-shaped crystals with micrometric size. Its structure at ambient temperature has already been reported but hydrogen atoms could not be identified from single-crystal X-ray diffraction. An analysis using 3D electron diffraction at low temperature brings to light the hydrogen positions and the existence of hydrogen disorder. At 100 K, kaatialaite is described in a monoclinic unit cell of = 15.46, = 19.996, = 4.808 Å, β = 91.64° and = 1485.64 Å with space group 2/. The hydrogen sites were revealed after refinements both considering the dynamical effects and ignoring them. The possibility to access most of the hydrogen positions, including partially occupied ones among heavy atoms, from the kinematical refinement is due to the recent developments in the analysis of 3D electron data. The hydrogen bonding observed in kaatialaite provides examples of HO configurations that have not been observed before in the structures of oxysalts with the presence of unusual inverse transformer HO groups.
来自捷克共和国雅希莫夫的矿物卡蒂亚莱特Fe[AsO(OH)]·5H₂O形成了微米级尺寸的白色针状晶体聚集体。其在室温下的结构已有报道，但通过单晶X射线衍射无法确定氢原子的位置。低温下的三维电子衍射分析揭示了氢的位置以及氢无序的存在。在100 K时，卡蒂亚莱特以单斜晶胞描述，其a = 15.46、b = 19.996、c = 4.808 Å，β = 91.64°，V = 1485.64 Å，空间群为2/m。在考虑动力学效应和忽略动力学效应的情况下进行精修后，揭示了氢的位置。通过运动学精修能够确定大多数氢的位置，包括重原子中部分占据的位置，这得益于三维电子数据分析的最新进展。在卡蒂亚莱特中观察到的氢键提供了HO构型的例子，这些构型在含氧酸盐结构中存在不寻常的反向变压器HO基团时以前未曾观察到。
