Cation‐site location in a natural chabazite
Cation‐site location in a natural chabazite
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天然菱沸石中的阳离子位点位置
DOI：
10.1107/s0567740882003483
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发表时间：
1982
期刊：
影响因子：
--
通讯作者：
P. C. Chiaramonti
中科院分区：
文献类型：
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作者：
M. Calligaris;G. Nardin;L. Randaccio;P. C. Chiaramonti
(Ca,Sr)菱沸石，Cal.aSro.3A13.sSis.3024.13H20，来自电子探针分析，菱面体，R3m，a = 9.421(4)A，a = 94.20(1)°，U = 829 A 3，Z = 1，g(Mo Ka) = 0.82 mm-~； 578 次独立反射的最终 R = 0.071。讨论了沿[ 1111 方向的三个阳离子位点和沸石笼中水分子的位置，并与之前基于二维分析得出的位置进行了比较。介绍。菱沸石是第 4 族的天然沸石，其骨架由双六元环 (D6R) 构成，并通过倾斜的四元环连接（图 1）。该框架包含 6.7 x 10 A 的大椭圆形空腔，由八元环进入（Breck，1974）。离子交换特性以及可交换阳离子在分子筛分特性中所发挥的作用证明了对菱沸石结构研究的兴趣（Mortier, Pluth & Smith, 1977a,b; Pluth, Smith & Mortier, 1977; Barrer, 1978）。另一方面，仅报道了水合天然菱沸石的二维 X 射线衍射分析（Smith、Rinaldi 和 Dent Glasser，1963；Smith、Knowles 和 Rinaldi，1964）。从这些结果表明，阳离子仅占据 x = 0.357、y = 0.494、z = 0.577 处的一个位点，因此晶体每个晶胞应包含 2 个钙离子和 13 个水分子。为了验证阳离子和水分子的这种排列，我们对天然菱沸石进行了三维 0567-7408/82/020602-04501.00 X 射线分析，作为与过渡金属离子交换的菱沸石结构研究的第一步。天然样本来自阿塞拜疆东北部、伊朗（Comin-Chiaramonti、Pongiluppi & Vezzalini，1979）。使用全自动 ARLSEMQ 仪器对八个菱沸石单晶进行波长色散微探针分析。表 1 给出了 24 个 O 原子的平均化学分析和原子比。化学分析表明菱沸石的锶含量特别丰富。
(Ca,Sr) chabazite, Cal.aSro.3A13.sSis.3024.13H20 from electron microprobe analysis, rhombohedral, R3m, a = 9.421(4)A, a = 94.20(1) °, U = 829 A 3, Z = 1, g(Mo Ka) = 0.82 mm-~; final R = 0.071 for 578 independent reflections. The location of three cation sites along the [ 1111 direction and of water molecules in the zeolitic cage is discussed and compared with that previously attributed on the basis of a two-dimensional analysis. Introduction. Chabazite is a natural zeolite of group 4, its framework being built up by double six-membered rings (D6R), linked by tilted four-membered rings (Fig. 1). The framework contains large ellipsoidal cavities of 6.7 x 10 A, entered by eight-membered rings (Breck, 1974). The ion-exchange properties and the role played by exchangeable cations in molecule-sieving properties justify the interest for a structural study of chabazites (Mortier, Pluth & Smith, 1977a,b; Pluth, Smith & Mortier, 1977; Barrer, 1978). On the other hand only two-dimensional X-ray diffraction analyses have been reported for hydrated natural chabazites (Smith, Rinaldi & Dent Glasser, 1963; Smith, Knowles & Rinaldi, 1964). From these results it was suggested that cations occupy but one site at x = 0.357, y = 0.494, z = 0.577, so that the crystal should contain two calcium ions and 13 water molecules per unit cell. To verify such an arrangement of cations and water molecules, we have undertaken the three-dimensional 0567-7408/82/020602-04501.00 X-ray analysis of a natural chabazite as the first step of a structural study of chabazites exchanged with transition-metal ions. The natural sample was from north-east Azerbaijan, Iran (Comin-Chiaramonti, Pongiluppi & Vezzalini, 1979). Wavelength dispersive microprobe analysis was carried out on eight single crystals of chabazite, using a fully automated ARLSEMQ instrument. The mean chemical analysis and the atomic ratios evaluated for 24 O atoms are given in Table 1. The chemical analysis indicates that the chabazite is particularly rich in strontium.