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首页> 外文期刊>Acta Crystallographica, Section B. Structural Science >Cristobalite-related phases in the NaAlO2-NaAlSiO4 system. II. A commensurately modulated cubic structure
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Cristobalite-related phases in the NaAlO2-NaAlSiO4 system. II. A commensurately modulated cubic structure

机译：NaAlO2-NaAlSiO4系统中与方石英有关的相。二。相称调制的立方结构

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摘要

The crystal structure of a new cubic cristobalite-related sodium aluminosilicate Na1.45Al1.45Si0.55O4 [P2(1)3, a = 14.553 (1) Angstrom] has been modelled using a modulation wave approach and the model tested against X-ray powder diffraction data using the Rietveld method. Owing to there being 64 independent positional parameters and eight independent Na sites, refinement of the tetrahedral framework atom positions and Na occupancies was not possible. The framework was modelled successfully in terms of q(1) = 1/4[020](p)*-type (p = parent) modulation waves with the requirement that the MO4 (M = Al0.725Si0.275) tetrahedra be as close to regular as possible. Na/vacancy ordering was modelled successfully in terms of q(2) = 1/4[220](p)* modulation waves. Only the Na-atom positions were refined. The significance of this unique modulated cubic cristobalite-related structure and the possible insight it provides to understanding beta-cristobalite are discussed. [References: 24]
机译：已使用调制波方法对新型立方方英石相关的铝硅酸钠Na1.45Al1.45Si0.55O4 [P2（1）3，a = 14.553（1）埃]的晶体结构进行了建模，并对该模型进行了X射线测试使用Rietveld方法的粉末衍射数据。由于有64个独立的位置参数和8个独立的Na位，因此无法对四面体框架原子位置和Na占位率进行改进。根据q（1）= 1/4 [020]（p）*型（p =母体）调制波成功建模了框架，并要求MO4（M = Al0.725Si0.275）四面体为尽可能接近常规。 Na /空位排序已成功建模为q（2）= 1/4 [220]（p）*调制波。仅钠原子的位置被精炼。讨论了这种独特的调制立方方石英相关结构的意义及其为理解β方石英提供的可能见解。 [参考：24]

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