Growth, structure and morphology study of monoclinic RbGd(WO4)2 crystals

The undoped rubidium gadolinium bis(tungstate) crystals, RbGd(WO4)2 (RGW), have been grown by the spontaneous nucleation from high-temperature solutions. The crystal structure has been refined at room temperature by using single-crystal X-ray diffraction data. The unit-cell parameters are a=10.6953(12) Å, b=10.5017(11) Å, c=7.6064(11) Å, β=130.504(7)°, with Z=4 in space group C2/c, which is a little difference with KGd(WO4)2. Crystal habits were predicted by the attachment energy model of Hartman and Perdok and we compared predictions to experimentally grown crystal shapes.