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Raman spectroscopic study of the selenite mineral mandarinoite Fe 2 Se 3 O 9 ·6H 2 O
Author(s) -
Frost Ray L.,
Keeffe Eloise C.
Publication year - 2009
Publication title -
journal of raman spectroscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.748
H-Index - 110
eISSN - 1097-4555
pISSN - 0377-0486
DOI - 10.1002/jrs.2070
Subject(s) - raman spectroscopy , chemistry , hydrogen bond , analytical chemistry (journal) , mineral , crystallography , molecule , physics , optics , organic chemistry , chromatography
Abstract Selenites and tellurites may be subdivided according to formula and structure. There are five groups, based upon the formulae (a) A(XO 3 ), (b) A(XO 3 ·) xH 2 O, (c) A 2 (XO 3 ) 3 ·xH 2 O, (d) A 2 (X 2 O 5 ) and (e) A(X 3 O 8 ). Of the selenites, molybdomenite is an example of type (a); chalcomenite, clinochalcomenite, cobaltomenite and ahlfeldite are minerals of type (b); mandarinoite Fe 2 Se 3 O 9 ·6H 2 O 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 (Se 3 O 9 ) 6− units. Three Raman bands observed at 695, 723 and 744 cm −1 are attributed to the ν 3 (Se 3 O 9 ) 6− anti‐symmetric stretching modes. Raman bands at 355, 398 and 474 cm −1 are assigned to the ν 4 and ν 2 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 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 It is probable that some of the selenite units have been replaced by hydroxyl units. Copyright © 2008 John Wiley & Sons, Ltd.