Ab InitioStructure Determination of New Rare Earth Fluoride BoratesLn3(BO3)2F3(Ln=Sm, Eu, and Gd)

The crystal structures ofLn3(BO3)2F3(Ln=Sm, Eu, and Gd) are determinedab initiofrom X-ray powder data. The unit cell is monoclinic, space groupC2/c,Z=4, witha=12.534(1) Å,b=6.237(1) Å,c=8.360(1) Å,β=97.404(6)°,V=648.1(2) Å3for Gd3(BO3)2F3. The Rietveld refinement reliability converged toRp=0.121,Rwp=0.147,Rexp=0.050,χ2=8.75. The structure presents a 3D network of Archimedian monocapped antiprisms Gd(1)O4F5and Gd(2)O7F2. These polyhedra form trimeric entities Gd3O12F9, which build infinite layers parallel to the (010) plane.