Dissymmetrization in Labuntsovite-Group Minerals. II: Refined Pm-Model of the Lemmleinite-Ba Crystal Structure

IF 0.5 4区材料科学 Q4 CRYSTALLOGRAPHY Crystallography Reports Pub Date : 2026-09-14 DOI:10.1134/S1063774525602011

R. K. Rastsvetaeva, V. M. Gridchina, N. V. Chukanov, S. M. Aksenov

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Abstract

Lemmleinite-Ba, a labuntsovite-group mineral with the ideal formula Na₄K₄Ba₂Ti₈(Si₄O₁₂)₄O₄(OH)₄⋅ 8H₂O, from the Kukisvumchorr mountain pegmatite of the Khibiny alkaline massif (Kola Peninsula), was investigated by X-ray diffraction analysis. The crystal structure of the mineral was previously studied within the centrosymmetric space group C2/m. It differs from the structures of other labuntsovite-group members in the ordered distribution of K and Ba. The monoclinic unit-cell parameters are a = 14.216(2) Å, b = 13.755(3) Å, c = 7.767(5) Å, β = 116.7(1)°, V = 1357(1) Å³. Lemmleinite-Ba was re-studied in the space group Pm. The structure was refined to R = 0.038 using 1934 observed reflections with F > 2σ(F). The transition to a model with reduced symmetry made it possible to identify subtle features of the distribution of cations over structural positions.

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labuntsote - group矿物中的不对称现象。lemmleite - ba晶体结构的精细pm模型

利用x射线衍射分析研究了Kola半岛Khibiny碱性地块Kukisvumchorr山伟晶岩中的lemmleite - ba矿物，其理想分子式为Na4K4Ba2Ti8(Si4O12)4O4(OH)4⋅8H2O。该矿物的晶体结构先前在中心对称空间群C2/m内进行了研究。它在K和Ba的有序分布上不同于其他的labuntsovite族成员的结构。单斜晶胞参数为a = 14.216(2) Å， b = 13.755(3) Å， c = 7.767(5) Å， β = 116.7(1)°，V = 1357(1) Å3。lemmleite - ba在空间组Pm中重新研究。利用1934年观测到的F >； 2σ(F)反射，将结构细化为R = 0.038。向对称性降低的模型的过渡使得识别阳离子在结构位置上分布的细微特征成为可能。

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来源期刊

Crystallography Reports 化学-晶体学

CiteScore

1.10

自引率

28.60%

发文量

审稿时长

4-8 weeks

期刊介绍： Crystallography Reports is a journal that publishes original articles short communications, and reviews on various aspects of crystallography: diffraction and scattering of X-rays, electrons, and neutrons, determination of crystal structure of inorganic and organic substances, including proteins and other biological substances; UV-VIS and IR spectroscopy; growth, imperfect structure and physical properties of crystals; thin films, liquid crystals, nanomaterials, partially disordered systems, and the methods of studies.