关键词: aluminium borate, Li$_{3}$AlB$_{2}$O$_{6}$, structure, molecule dynamics simulation

Abstract: A new compound with the same chemical composition as Li$_{3}$AlB$_{2}$O$_{6}$ but with a different x-ray powder diffraction pattern as reported before was synthesized and studied experimentally by M. He, Chen X L et al (J. Solid State Chem. 163, 369 (2002)), but there lacks first principles study on the structure of it. Using conjugant gradient (CG) molecule dynamics (MD) simulation with a full relaxation of the atomic positions and of the shape and size of the cell, the structure of Li$_{3}$AlB$_{2}$O$_{6}$ is studied from first principles. For the density functional, the local density approximation (LDA) and the generalized gradient approximation (GGA) forms are used respectively. Both the LDA and GGA results support the experimental structure of M. He et al. The result of MD simulation using GGA agrees with the experimental result much better. The energy bands are also studied, the band gap given by LDA and GGA are 5.65 eV, 5.34eV, respectively.

Key words: aluminium borate, Li$_{3}$AlB$_{2}$O$_{6}$, structure, molecule dynamics simulation