Ab initio structure determination of new compound LiAlB2O5

A new compound LiAlB2O5 has been synthesized by solid-state reaction and it s structure has been solved ab initio from X-ray powder diffraction data. T he structure determination was based on direct methods combined with differ ence-Fourier techniques and the refinement was carried out using the Rietve ld method. The final refinement converged with R-p = 6.95%, R-wp = 9.43%, R -exp = 3.93%. This compound belongs to the monoclinic space group C2/c, wit h lattices parameters a = 9.9096(1) Angstrom, b = 10.0634(1) Angstrom, c = 9.3552(1) Angstrom, and beta = 120.0681(3). There are eight molecules per u nit cell and 10 atoms in the asymmetric unit. The structure of LiAlB2O5 exh ibits some similarities to that of LiB3O5. Structural units found in LiAlB2 O5, [B2AlO7](5-) groups, can be described as [B3O7](-5) with the tetra-coor dinated B replaced by an Al atom, which may possess higher second-order mic roscopic susceptibility than [B3O7](5-). (C) 2001 Academic Press.