Molecular structure of the uranyl mineral uranopilite—a Raman spectroscopic study

Raman spectroscopy of the mineral uranopilite at 298 and 77 K has been obtained and used to elucidate the structure of the mineral at the molecular level. A single intense band at 1010 cmK1 is assigned to the n1 (SO4)2K symmetric stretching mode. Three low intensity bands in the 298 K Raman spectrum are observed at 1143, 1117 and 1097 cmK1 and in the 77 K spectrum four bands at 1148, 1130, 1118 and 1106 cmK1. These bands are attributed to the n3 antisymmetric stretching modes. A series of infrared bands are found at 1559, 1540, 1526 and 1511 cmK1 attributed to d UOH bending modes. Three bands are observed at 843, 835 and 819 cmK1 in both 298 and 77 K spectra attributed to the n1 symmetric stretching modes of the (UO2)2C units. In the infrared spectra bands are observed at 941, 929 and 910 cmK1 and are assigned to the n3 antisymmetric stretching modes of the UO2 units. These values are used to calculate UO bond distances. Multiple OH stretching modes prove a complex arrangement of OH groupings, i.e. water molecules and OHK ions, and hydrogen bonding in the crystal structure of uranopilite. q 2004 Elsevier B.V. All rights reserved