硫化锂分子的分析势能函数和光谱

应用密度泛函理论的B3LYP方法和6-311++g（d，p）基组，研究Li₂、LiS和Li₂S分子的基态构型.结果表明它们的基电子态分别为X¹Σ_g⁺、X²Π和X¹Σ_g⁺.通过非线性曲线拟合，得到基态LiS和Li₂分子的4参数Murrell-Sorbie分析势能函数，计算它们的光谱参数和力常数.基于多体项展式理论得到了基态Li₂S分子的单重态势能面的分析函数.利用得到的分析势能函数重构基态单重Li₂S分子的旋转图、伸缩图和旋转伸缩图，准确地再现了Li₂S分子的静态特征，如平衡结构，最低能量，合理反应通道.从等值势能面图看出，反应Li+S+Li→Li₂S是一个无阈值反应.S原子攻击Li₂分子的反应通道上，有一个过渡态.Li原子攻击LiS分子通道上也有一个过渡态.

Analytical Potential Energy Function and Spectra of Li2 S Molecule

Structures of ground states of Li₂, LiS and Li₂S molecules are investigated using density function theory B3LYP method and 6-311++g(d,p) basis set. It shows that their electronic states are X¹Σ_g⁺, X²Π_g and X¹Σ_g⁺. Murrell-Sorbie potential functions with 4 parameters for LiS and Li₂ molecules are obtained with nonlinear curve fitting method. Spectral parameters and force constants are studied with Murrel-Sobie potential functions. Analytical potential surface of singlet Li₂S is obtained with many-body expansion theory. Rotary contour map, stretching contour map and rotary stretching contour map are reconstructed with analytical potential surface. Static characters of ground singlet Li₂S are repeated exactly through these maps. They are equilibrium geometric structure, lowest energy and reasonable chemical reaction channels, respectively. Stretching vibrational contours of potential energy surface show that reaction Li+S+Li→Li₂S is a no barrier reaction channel. Reaction channel of S atom attacking Li₂ molecule has a transition state. Channel of Li atom attacking LiS molecule has a transition state.