存储基集
基准集
高斯分布
化学
分子轨道
价(化学)
原子物理学
碎片分子轨道
缩放比例
氢原子
多原子离子
基函数
分子轨道理论
分子
非键轨道
分子物理学
计算化学
物理
量子力学
密度泛函理论
数学
群(周期表)
几何学
有机化学
作者
R. Ditchfield,Warren J. Hehre,John A. Pople
摘要
An extended basis set of atomic functions expressed as fixed linear combinations of Gaussian functions is presented for hydrogen and the first-row atoms carbon to fluorine. In this set, described as 4–31 G, each inner shell is represented by a single basis function taken as a sum of four Gaussians and each valence orbital is split into inner and outer parts described by three and one Gaussian function, respectively. The expansion coefficients and Gaussian exponents are determined by minimizing the total calculated energy of the atomic ground state. This basis set is then used in single-determinant molecular-orbital studies of a group of small polyatomic molecules. Optimization of valence-shell scaling factors shows that considerable rescaling of atomic functions occurs in molecules, the largest effects being observed for hydrogen and carbon. However, the range of optimum scale factors for each atom is small enough to allow the selection of a standard molecular set. The use of this standard basis gives theoretical equilibrium geometries in reasonable agreement with experiment.
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