title: Assessment of the molecular structure of the borate mineral sakhaite Ca12Mg4(BO3)7(CO3)4Cl(OH)2·H2O using vibrational spectroscopy.
abstract: The structure of the borate mineral sakhaite Ca(12)Mg(4)(BO(3))(7)(CO(3))(4)Cl(OH)(2)·H(2)O, a borate-carbonate of calcium and magnesium has been assessed using vibrational spectroscopy. Assignment of bands is undertaken by comparison with the data from other published results. Intense Raman band at 1134 cm(-1) with a shoulder at 1123 cm(-1) is assigned to the CO(3)(2-) symmetric stretching mode. The Raman spectrum displays bands at 1479, 1524 and 1560 cm(-1) which are assigned to the CO(3)(2-) antisymmetric stretching vibrations. The observation of multiple carbonate stretching bands supports the concept that the carbonate units are non-equivalent. The Raman band at 968 cm(-1) with a shoulder at 950 cm(-1) is assigned to the symmetric stretching mode of trigonal boron. Raman bands at 627 and 651 cm(-1) are assigned to the out-of-plane bending modes of trigonal and tetrahedral boron. Raman spectroscopy coupled with infrared spectroscopy enables the molecular structure of the mineral sakhaite to be assessed.
authors.affiliation: Chemistry Discipline, Science and Engineering Faculty, Queensland University of Technology, GPO Box 2434, Brisbane, Queensland 4001, Australia. r.frost@qut.edu.au
authors.forename: Ray L
authors.initials: RL
authors.lastname: Frost
authors.forename: Yunfei
authors.initials: Y
authors.lastname: Xi
mesh_terms: D001881:Borates / Q000737:chemistry*; D008903:Minerals / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D013059:Spectrum Analysis, Raman; D014732:Vibration
chemical_list: D001881:Borates; D008903:Minerals