Abstract

The crystallographic analysis of three modifications of CaCO₃ – rhombohedral calcite (\(R\bar{3}c\)), orthorhombic aragonite (Pmcn), and monoclinic vaterite (C2/c) – reveals different mechanisms of atomic ordering in the structures. An important role in the formation of a specific structure is played by the point symmetry of energetically stable atomic groups (templates) in the precrystallization phase, which depends on the crystallization conditions, impurities, and local heterogeneities. Then the template symmetry forms the structure symmetry by placing heavy atoms and mass centers of stable CO₃ atomic groups mainly in special positions with fixed coordinates. The details of this crystal dynamics (the ordering of atomic positions by translational and point symmetries) are shown.

中文翻译：

---

CaCO3 三种改性的晶体学分析：方解石、文石、球霰石

摘要

CaCO ₃的三种变体——菱形方解石（\(R\bar{3}c\)）、斜方文石（Pmcn）和单斜球霰石（C 2/ c）——的晶体学分析揭示了不同的原子排序机制结构。预结晶阶段中能量稳定原子团（模板）的点对称在特定结构的形成中起着重要作用，这取决于结晶条件、杂质和局部异质性。然后模板对称通过将重原子和稳定的CO ₃原子团的质心主要放置在具有固定坐标的特殊位置来形成结构对称。这个的详细显示了晶体动力学（通过平移和点对称性对原子位置进行排序）。