CaSiO₃ polymorphs are abundant in only unique geological settings on the Earth’s surface and are the major Ca-bearing phases at deep mantle condition. An accurate and comprehensive study of their density and structural evolution with pressure and temperature is still lacking. Therefore, in this study we report the elastic behavior and structural evolution of wollastonite and CaSiO₃-walstromite with pressure. Both minerals are characterized by first order phase transitions to denser structures. The deformations that lead to these transformations allow a volume increase ofthe bigger polyhedra, which might ease cation substitution in the structural sites of these phases. Furthermore, their geometrical features are clear analogies with those predicted and observed for tetrahedrally-structured ultra-high-pressure carbonates, which are unfortunately unquenchable. Indeed, wollastonite and CaSiO₃-walstromite have a close resemblance to ultra-high-pressure chain- and ring-carbonates. This suggests a rich polymorphism also for tetrahedral carbonates, which might increase the compositional range of these phases, including continuous solid solutions involving cations with different size (Ca vs. Mg in particular) and important minor or trace elements incorporation.

中文翻译：

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CaSiO3 多晶型物在地幔压力下的晶体结构演变

CaSiO ₃多晶型物仅存在于地球表面独特的地质环境中，并且是深部地幔条件下的主要含钙相。仍然缺乏对它们的密度和结构随压力和温度的演变进行准确而全面的研究。因此，在本研究中，我们报告了硅灰石和 CaSiO ₃的弹性行为和结构演变。- 带压力的硅藻土。这两种矿物的特点是一级相变到更致密的结构。导致这些转变的变形允许更大的多面体的体积增加，这可能会减轻这些相结构位置中的阳离子取代。此外，它们的几何特征与预测和观察到的四面体结构超高压碳酸盐的几何特征明显相似，不幸的是，这些特征是不可淬火的。事实上，硅灰石和 CaSiO ₃-walstromite 与超高压链状和环状碳酸盐非常相似。这表明四面体碳酸盐也具有丰富的多晶性，这可能会增加这些相的组成范围，包括涉及不同尺寸阳离子（特别是 Ca 与 Mg）的连续固溶体以及重要的微量元素或微量元素的结合。