Rcaction mechanism between Mg(NH₂)₂ and LiH are investigated with a B3LYP method of density functional theory. Geometries and harmonic vibration frequencies of reactants,intermediates,transition states and products are calculated at B3LYP/6-311G(d,P) level.Vibration analysis and intrinsic reaction coordinates(IRC) calculation at the same level are applied to validate connection of stationarv points. It indicates that the reaction has three stages.They are the first step of hydrogen substitution,the second step of hydrogen substitution and isomerization after removal of hydrogen.There are two pathways, in which a channel of the second step of alignment hydrogen suhstitution reaction is the main channel.The two hydrogen atoms in H₂ released are from Mg(NH₂)₂ and Lilt.

Possible geometrical structures and relative stability of (MgB₂)_n(n=1~3) clusters are studied with a hybrid density functional theory(B3LYP) with 6-31G^* basis sets.For the stablest isomers of (MgB₂)_n(n=1~3) clusters,the electronic structure,vibrational property,bond,ionization potential,polarizability and hyperpolarizability are analyzed. Most of the optimized (MgB₂)_n(n=1~3) clusters are planar structures and the B-B and B-Mg bonds coexist,while the Mg-Mg bonds are infrequent.The bond lengths of B-B and Mg-B are 0.153~0.182 nm and 0.218~0.231 nm,respectively. Several negative B atoms form an electronegative center and other B and Mg atoms with positive charge are located at the apex of the cluster.The natural charges of Mg atom and B atom are +0.559e~+0.920e and -0.724e~+0.197e,respectively.