The crystal structures of 19 samples from the nepheline (NaAlSiO4; Ne)–kalsilite (KAlSiO4; Ks) series, previously prepared via ion-exchange, were examined using synchrotron high-resolution powder X-ray diffraction (HRPXRD) data and Rietveld structure refinements. Parent materials for the three series include a natural Monte Somma nepheline (series-1), synthetic Na nepheline (series-2), and high-Si synthetic nepheline (series-3), having excess Si mole percentages of 5.2, 1.7, and 12.5%, respectively. Three different structure-types were found to occur among the samples examined: nepheline (P63), tetrakalsilite (P63), and kalsilite (both P63 and P31c intergrowth). Trikalsilite was not observed in this study. Vacancies (☐) at the K site as well as Ca and K atoms at the Na1 site play an important role in the crystal-chemical behavior of nepheline solid solutions. Vacancies cause an elongation in the average [9] distance in nepheline. When K atoms enter the Na1 site in nepheline, the average <(Na,K)-O>[7] distance increases linearly and is parallel to the average <(Na,K)-O>[9] distance in kalsilite and the grand mean of such distances in trikalsilite and tetrakalsilite. Before K atoms enter the Na1 site, the average <(Na,K)-O>[7] distance is constant because of the full occupancy of the Na1 site with Na atoms. Ca atoms at the Na1 site in the Monte Somma sample-1 cause a contraction in the <(Na,K)-O>[7] distance. In Na-rich nepheline samples, Na atoms in the large channels occupy a Na(K) site that is off the 63 axis and close to the usual K site. In natural nepheline samples, the K site in most cases contains K atoms and ☐, and the Na1 site is filled mainly with Na, minor Ca, and K atoms in K-rich samples. Nepheline from Monte Somma (sample-1) contains weak satellite reflections that are also present in some other kalsilite samples. Average distances indicate a high degree of Al-Si disorder in nepheline but increasing Al-Si order in tetrakalsilite and kalsilite. Increasing the amount of K atoms beyond the ideal composition of K0.25Na0.75[AlSiO4] causes expansion in multiple structural parameters because of the larger size of K+ relative to Na+.

中文翻译：

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霞石（NaAlSiO4）–钾硅石（KAlSiO4）系列的结构变化

使用同步加速器高分辨率粉末X射线衍射（HRPXRD）数据和Rietveld结构细化，检查了以前通过离子交换制备的19个霞石（NaAlSiO4; Ne）-方解石（KAlSiO4; Ks）系列样品的晶体结构。 。这三个系列的母体材料包括天然Monte Somma霞石（系列1），合成Na霞石（系列2）和高Si合成霞石（系列3），其Si摩尔百分比分别为5.2、1.7和1.0。分别为12.5％。发现在所检查的样品中出现三种不同的结构类型：霞石（P63），四方硅铝石（P63）和方钠石（P63和P31c共生）。在这项研究中未观察到三方硅铝石。K位的空位（☐）以及Na1位的Ca和K原子在霞石固溶体的晶体化学行为中起重要作用。空缺导致平均伸长率[9]霞石中的距离。当K原子进入霞石中的Na1位点时，平均<（Na，K）-O> [7]距离线性增加，并且平行于钾铝矿和硅藻土中的平均<（Na，K）-O> [9]距离。在三方硅铝石和四方硅铝石中这种距离的大平均值。在K原子进入Na1位置之前，平均<（Na，K）-O> [7]距离是恒定的，因为Na1位置完全被Na原子占据。Monte Somma sample-1的Na1位置的Ca原子引起<（Na，K）-O> [7]距离的收缩。在富含Na的霞石样品中，大通道中的Na原子占据了一个Na（K）位点，该位点偏离63轴并靠近通常的K位点。在天然霞石样品中，大多数情况下K位置包含K原子和☐，而Na1位置在富含K的样品中主要填充有Na，次要Ca和K原子。来自蒙特索玛（Monte Somma）的霞石（样品1）含有弱的卫星反射，这在其他一些钾盐岩样品中也存在。平均数距离表明霞石中的Al-Si杂乱程度很高，但四方硅铝石和钾铝石中的Al-Si有序增加。将K原子的数量增加到超过K0.25Na0.75 [AlSiO4]的理想组成会导致多个结构参数的膨胀，因为K +相对于Na +的尺寸较大。