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In the present study,we apply Monte Carlo method to predict the crystal structure of Li2 Ti(BH4)5(NH3)5(abbreviated as ATLB)By using DFT method,we optimized the structure and obtain its electronic structure and bond population.In the calculation,the generalized gradient approximation [1] of Perdew,Burke and Erzerhof [2](GGA-PBE)for the exchange-correlation function has been used throughout.The Vanderbilt-type ultrasoft pseudopotentials [3] with valence states 3s2 3p6 4s2 3d2 for Ti,1s2 2s1 for Li,2s2 2p1 for B,2s2 2p3 for N,and 1s1 for H were used to describe the core electrons.A plane wave basis set with an energy cutoff of 500eV has been used.Based on the experiment study of ATLB [4],it is a very promising bimetallic AMB because there is no contamination in the decomposition.About 9%pure hydrogen can be librated within 400 min at 100℃.Fig.1 shows the predicted cell structures of ATLB.The crystal ATLB adopts orthorhombic symmetry in space group P222 with the cell parameters of a= 8.8653,b= 13.4715 and c= 13.7825.In crystalline ATLB,each Li + is coordinated to three [BH4]-groups through B which is parallel with the 100 planar.Actually,there is one [BH4] group is shared by Ti3+ and Li +.And each Ti3+ is hexahedron coordinated to five [NH3] groups through N and one [BH4] group through B.