Ab initio structure determination of new compound Li4CaB2O6

A new compound, Li4CaB2O6, has been synthesized by solid-state reaction and its structure has been determined from powder X-ray diffraction data by direct methods. The refinement was carried out using the Rietveld methods and the final refinement converged with Rp=10.4%, Rwp=14.2%, Rexp=4.97%. This compound belongs to the orthorhombic space group Pnnm, with lattice parameters a=9.24036(9) A, b=8.09482(7) A, and c=3.48162(4) A. Fundamental building units are isolated [BO3]3- anionic groups, which are all parallel to the a-b plane stacked along the c-axis. The Ca atoms are six-coordinated by the O atoms to form octahedral coordination polyhedra, which are joined together through edges along the c-axis, forming infinitely long three-dimensional chains. The Li atoms have a four-fold and a five-fold coordination with O atoms that lead to complex Li-O-Li chains that also extend along the c-axis. The infrared spectrum of Li4CaB2O6 was also studied, which is consistent with the crystallographic study