Raman spectroscopic study of the selenite mineral mandarinoite Fe2Se3O9•6H2O
Selenites and tellurites may be subdivided according to formula and structure. There are five groups, based upon the formulae (a) A(XO3), (b) A(XO3).xH2O, (c) A2(XO3)3.xH2O, (d) A2(X2O5) and (e) A(X3O8). Of the selenites, molybdomenite is an example of type (a); chalcomenite, clinochalcomenite, cobaltomenite and ahlfeldite are minerals of type (b); mandarinoite Fe2Se3O9•6H2O is an example of type (c). Raman spectroscopy has been used to characterise the mineral mandarinoite. The intense, sharp band at 814 cm-1 is assigned to the symmetric stretching (Se3O9)6- units. Three Raman bands observed at 695, 723 and 744 cm-1 are attributed to the ν3 (Se3O9)6- antisymmetric stretching modes. Raman bands at 355, 398 and 474 cm-1 are assigned to the ν4 and ν2 bending modes. Raman bands are observed at 2796, 2926, 3046, 3189 and 3507 cm-1 and are assigned to OH stretching vibrations. The observation of multiple OH stretching vibrations suggests the non-equivalence of water in the mandarinoite structure. The use of the Libowitzky empirical function provides hydrogen bond distances of 2.633(9) Å (2926 cm-1), 2.660(0) Å (3046 cm-1), 2.700(0) Å (3189 cm-1) and 2.905(3) Å (3507 cm-1). The observation of multiple water stretching bands supports the concept of non-equivalent water units in the mandarinoite structure. The sharp, intense band at 3507 cm-1 may be due to hydroxyl units. It is probable that some of the selenite units have been replaced by hydroxyl units.
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|Item Type:||Journal Article|
|Keywords:||selenite, Raman spectroscopy, mandarinoite, schmiederite, chalcomenite, clinochalcomenite|
|Subjects:||Australian and New Zealand Standard Research Classification > CHEMICAL SCIENCE (030000) > PHYSICAL CHEMISTRY (INCL. STRUCTURAL) (030600) > Structural Chemistry and Spectroscopy (030606)|
|Divisions:||Past > QUT Faculties & Divisions > Faculty of Science and Technology|
Past > Schools > School of Physical & Chemical Sciences
|Copyright Owner:||Copyright 2009 John Wiley & Sons, Ltd|
|Copyright Statement:||The definitive version is available at www3.interscience.wiley.com|
|Deposited On:||02 Feb 2009 13:10|
|Last Modified:||01 Mar 2012 00:07|
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