School of Chemistry, Physics and Mechanical Engineering, Science and Engineering Faculty, Queensland University of Technology, GPO Box 2434, Brisbane, Queensland 4001, Australia.
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. 2014 Mar 25;122:400-4. doi: 10.1016/j.saa.2013.11.020. Epub 2013 Nov 21.
Vibrational spectroscopy enables subtle details of the molecular structure of kapundaite to be determined. Single crystals of a pure phase from a Brazilian pegmatite were used. Kapundaite is the Fe(3+) member of the wardite group. The infrared and Raman spectroscopy were applied to compare the structure of kapundaite with wardite. The Raman spectrum of kapundaite in the 800-1400 cm(-1) spectral range shows two intense bands at 1089 and 1114 cm(-1) assigned to the ν1PO4(3-) symmetric stretching vibrations. The observation of two bands provides evidence for the non-equivalence of the phosphate units in the kapundaite structure. The infrared spectrum of kapundaite in the 500-1300 cm(-1) shows much greater complexity than the Raman spectrum. Strong infrared bands are found at 966, 1003 and 1036 cm(-1) and are attributed to the ν1PO4(3-) symmetric stretching mode and ν3PO4(3-) antisymmetric stretching mode. Raman bands in the ν4 out of plane bending modes of the PO4(3-) unit support the concept of non-equivalent phosphate units in the kapundaite structure. In the 2600-3800 cm(-1) spectral range, Raman bands for kapundaite are found at 2905, 3151, 3311, 3449 and 3530 cm(-1). These bands are broad and are assigned to OH stretching vibrations. Broad infrared bands are also found at 2904, 3105, 3307, 3453 and 3523 cm(-1) and are attributed to water. Raman spectroscopy complimented with infrared spectroscopy has enabled aspects of the structure of kapundaite to be ascertained and compared with that of other phosphate minerals.
振动光谱能够确定 kapundaite 分子结构的细微细节。使用了来自巴西伟晶岩的纯相单晶。kapundaite 是 wardite 族的 Fe(3+)成员。红外和拉曼光谱被应用于比较 kapundaite 和 wardite 的结构。kapundaite 的拉曼光谱在 800-1400 cm(-1)光谱范围内显示出两个在 1089 和 1114 cm(-1)处的强带，归因于 ν1PO4(3-)对称伸缩振动。两个带的观察为 kapundaite 结构中磷酸盐单元的不等价提供了证据。kapundaite 的红外光谱在 500-1300 cm(-1)范围内显示出比拉曼光谱更大的复杂性。在 966、1003 和 1036 cm(-1)处发现了强的红外带，归因于 ν1PO4(3-)对称伸缩模式和 ν3PO4(3-)反对称伸缩模式。PO4(3-)单元的 ν4 面外弯曲模式中的拉曼带支持 kapundaite 结构中不等价磷酸盐单元的概念。在 2600-3800 cm(-1)光谱范围内，kapundaite 的拉曼带位于 2905、3151、3311、3449 和 3530 cm(-1)。这些带很宽，归因于 OH 伸缩振动。在 2904、3105、3307、3453 和 3523 cm(-1)处也发现了宽的红外带，归因于水。拉曼光谱与红外光谱相结合，使 kapundaite 的结构方面得以确定，并与其他磷酸盐矿物的结构进行了比较。
