Raman spectroscopic study of the mineral finnemanite Pb5(As3+O3)3Cl

Abstract

AbstractThe arsenite mineral finnemanite Pb5(As3+ O3)3Cl has been studied by Raman spectroscopy. The most intense Raman band at 871 cm−1 is assigned to the ν1(AsO3)3− symmetric stretching vibration. Three Raman bands at 898, 908 and 947 cm−1 are assigned to the ν3(AsO3)3− antisymmetric stretching vibration. The observation of multiple antisymmetric stretching vibrations suggest that the (AsO3)3− units are not equivalent in the molecular structure of finnemanite. Two Raman bands at 383 and 399 cm−1are assigned to the ν2(AsO3)3− bending modes. Density functional theory enabled calculation of the position of AsO32− symmetric stretching mode at 839 cm−1, the antisymmetric stretching mode at 813 cm−1 and the deformation mode at 449 cm−1. Raman bands are observed at 115, 145, 162, 176, 192, 216 and 234 cm−1 as well. The two most intense bands are observed at 176 and 192 cm−1. These bands are assigned to PbCl stretching vibrations and result from transverse/longitudinal splitting. The bands at 145 and 162 cm−1 may be assigned to ClPbCl bending modes. Copyright © 2009 John Wiley & Sons, Ltd.