基态MgB2分子的结构与分析势能函数

应用群论及原子分子反应静力学方法推导MgB₂分子的电子状态及其离解极限,采用密度泛函B3LYP和从头计算QCISD方法在6-311++G**基组水平上,对MgB₂分子可能的状态进行优化计算,得出MgB₂的三重态能量最低,其稳定构型为C_2v,平衡核间距R_e=2.2977，键角α_BMgB=41.5521°,能量为-248.9645a.u.同时还计算了基态的简正振动频率:对称伸缩振动频率ν（B₂）=315.4430 cm^-1,反对称伸缩振动频率ν（A₁）=418.1883 cm^-1和弯曲振动频率ν（A₁）=968.9672 cm^-1.在此基础上,使用多体项展式理论方法,导出了基态MgB₂分子的解析势能函数,其等势面准确再现了基态MgB₂平衡结构和离解能,并由此讨论了B+MgB和Mg+BB分子反应的势能面静态特征. 关键词： 2')" href="#">MgB₂ 多体项展式理论 解析势能函数

Molecule structure and analytical potential energy function for the ground state of MgB_2

Ab initio methods and density functional theory B3LYP with QCISD/6-311 + + G ** basis set have been used to calculate the equilibrium geometries and vibrational properties of the possible structures and electronic states of MgB_2 molecule. The present computational results predict that the ground electronic state is the triplet state~3 B_1 of C_(2v), (B-Mg-B) with equilibrium geometry R_e= 2.2977(A), α_(BMgB) = 41.5521°and the energy of the ground state~3 B_1 is -248.9645 a.u.. Similarly, the harmonic frequency has been calculated. Then, the analytic potential energy function of MgB_2 molecule is derived by many-body expansion theory for the first time. The contours of the potential energy surface are constructed, which clearly reproduce the character of the accurate equilibrium structure and dissociation energy for MgB_2 molecule. Furthermore, the molecular static reaction pathway is investigated based on this potential energy function.