Theoretical Study on the Structure and Stabilization of AlB₃ and Alb₃⁺

Ab initio molecular orbital calculations have been carried out with GAUSSIAN-92 program.The structures of AlB₃ and AlB₃⁺ were completely optimized within assumed symmetries using the restricted Hartree-Fock（RHF）method and the unrestricted one（RHF）.The effects of electron correlations using the Moller-Plesset perturbation theory to the second order.For above singlet structures with ＜s²＞ values,a modified AUSSIAN-92 version was used that annhilates this spin contamination（AUHF）.Vibrational frequencies were calculated analytically at HF/6-31G^*.The all HF/6-31G^* geometrical parameters and total energies for AlB₃ and AlB₃⁺ were listed in Tables 1and 2,with MP2 total energies and frequencies of partial isomers of AlB₃/AlB₃⁺ with more stable tabulated in Tables 3 and 4.On the basis of all these results,the stability law of AlB₃ and AlB₃⁺ has been known with C _3V （1A₁） is the most stable structure of AlB₃ isomers,and C_2V^（1） （²A₁） is the most one of AlB₃⁺.