School of Chemistry, Physics and Mechanical Engineering, Science and Engineering Faculty, Queensland University of Technology, GPO Box 2434, Brisbane, Queensland 4001, Australia.
Spectrochim Acta A Mol Biomol Spectrosc. 2013 Dec;116:204-8. doi: 10.1016/j.saa.2013.07.015. Epub 2013 Jul 23.
We have studied the mineral goyazite using Raman and infrared spectroscopy. Goyazite is a member of the crandallite subgroup of the alunite supergroup. The crystal structure is of the alunite-type and consists of sheets of corner-sharing AlO6 octahedra parallel to (0001). The octahedrally coordinated Sr(2+) cations occupy cavities between pairs of octahedral sheets and are surrounded by six oxygen atoms from the Al(3+)O6 octahedra. The very intense sharp band at 983 cm(-1) is assigned to the ν1PO4(3-) symmetric stretching mode. The observation of a single band supports the concept that all the phosphate units are equivalent in the structure of goyazite. Raman bands observed at 1029 cm(-1) and 1037 cm(-1) are assigned to the ν3PO4(3-) antisymmetric stretching vibrations. Two Raman bands at 895 and 927 cm(-1) are attributed to the stretching vibrations of H2PO4; thus indicating some hydrogen phosphate units in the structure of goyazite. Raman bands at 556, 581, 596 and 612 cm(-1) are assigned to the ν4PO4(3-) bending modes, suggesting a reduction of symmetry of phosphate units. Two sharp Raman bands at 3609 and 3631 cm(-1) are attributed to OH stretching vibrations from the goyazite hydroxyl units. Broad Raman bands at 2924, 3043, 3210, 3429 and 3511 cm(-1) are assigned to water stretching vibrations. This research shows that from a vibrational spectroscopic point of view, the formula SrAl3(H PO4,PO4)2(OH)6 · H2O is a better formulation for the mineral goyazite. Vibrational spectroscopy enables subtle details of the molecular structure of goyazite to be determined.
我们使用拉曼和红外光谱研究了矿物硅钙钡石。硅钙钡石是明矾石超族中克兰德尔石亚族的一员。晶体结构属明矾石型，由沿(0001)平行排列的共用角的 AlO6 八面体片层组成。八面体配位的 Sr(2+)阳离子占据八面体片层之间的空隙，并被来自 Al(3+)O6 八面体的六个氧原子所包围。在 983cm(-1)处非常尖锐的强带被分配给 ν1PO4(3-)对称伸缩模式。单一带的观察支持了所有磷酸根单元在硅钙钡石结构中都是等价的概念。在 1029cm(-1)和 1037cm(-1)处观察到的拉曼带被分配给 ν3PO4(3-)反对称伸缩振动。在 895 和 927cm(-1)处的两个拉曼带归因于 H2PO4 的伸缩振动；因此表明在硅钙钡石结构中有一些磷酸氢根单元。在 556、581、596 和 612cm(-1)处的拉曼带被分配给 ν4PO4(3-)弯曲模式，表明磷酸根单元的对称性降低。在 3609 和 3631cm(-1)处的两个尖锐的拉曼带归因于硅钙钡石羟基单元的 OH 伸缩振动。在 2924、3043、3210、3429 和 3511cm(-1)处的宽拉曼带被分配给水的伸缩振动。这项研究表明，从振动光谱的角度来看，SrAl3(HPO4,PO4)2(OH)6·H2O 是硅钙钡石的一个更好的分子式。振动光谱能够确定硅钙钡石分子结构的细微细节。
