Structural and spectroscopic properties of self-activated monoclinic molybdate BaSm2(MoO4)4

Abstract

Crystal structure of new monoclinic molybdate BaSm2(MoO4)4 is refined in monoclinic unit cell C2/m with cell parameters a=5.29448 Å, b=12.7232 Å, c=19.3907 Å, beta=91.2812 º, V= 1305.89 Å3. Crystal structure consists of SmO8 square antiprism joined with each other by edges forming 2D layer perpendicular to c-axis. MoO4 tetrahedra join to SmO8 by nodes and also participate in formation of layer, and Ba ions are located between these layers. Lattice dynamics is theoretically calculated on the base of crystal structure data. Raman spectra are recorded and analyzed in comparison with theoretical calculations. Discrepancy between the experimental and calculated Raman frequencies does not exceed 2 cm1 for the most of Raman lines. Luminescence spectra of Sm ions, which positioned in the lowest local symmetry site C1, strongly differ from those detected for another molybdate crystal, β-RbSm(MoO4)2, with C2 local symmetry. 4G5/2 → 6H9/2 band is dominating in the luminescence of BaSm2(MoO4)4.