Crystal structure of the new borate Li_3Gd(BO_3)_(2 centre dot) Comparison with the homologous Na_3Ln(BO_3)_2 (Ln: La, Nd) compounds

摘要

The structure of Li_3Gd(BO_3)_2 has been solved by X-ray diffraction study on single crystal. This novel borate crystallizes in the monoclinic system with the P2_1/c space group (Z = 4). The cell parameters are respectively equal to a = 8.724(2), b = 6.425(2), c = 10.095(2) A and #beta# = 116.85(2) deg. Refinements of 110 parameters using 2924 independent reflections having I > 2#sigma# (I) converged to R_1 = 0.028 (w R_2 = 0.058). The structure of Li_3Gd(BO_3)_2 is made up of double layers of eightfold coordinated Gd atoms parallel to the (bc) plane. They are linked by respectively three- and four-coordinated boron and lithium atoms. The structure is compared to that of the homologous sodium compounds, Na_3Ln(BO_3)_2 (Ln: La, Nd), in which LnO_8 polyhedra also form a bi-dimensional array.