The Influence Of Nuclear Distance And Power Exponent On Gauss Function Dual-center Overlap Integral

A widely used and widely criticized method to analyze SCF wave functions is population analysis, introduced.by Mullilken. He proposed a method that apportions the electrons of an n-electron molecule into net populations and overlap populations, and split cach overlap populations equally into two parts. But the equation method is unreasonable in some cases, so it is necessary to study the overlap region. The paper studies the main factor which influence the overlap integral of Mulliken population analysis.In this paper, Gaussian product theorem and the Fortran programme are used to calculate the overlap integral of two Gaussian functions, the dual-center integral, and discuss the influence factor of overlap integral in detail. First of all, take the most simple diatomic molecule H2for example to study the orbital overlap of Is-Is. By changing the distance between two atoms in the case of a fixed orbital exponent to determine the impace of the single variable R to the overlap integral. In the general trendency, use the control variable method again, the fixed-R range, to observe the changes of overlap integral which caused by orbital exponent. In this section, by changing the basis set to compare the distribution of electrons in different basis sets. Secondly, make use of the same method to discuss the overlap integral of heteronuclear diatomic molecule HF1s-2p orbital and get the rule of the orbital exponent in different range of the overlap integral changes with the interatomic distance R. At the same time, by changing the basis set to compare the distribution of electrons in different basis sets, and get that for heteronuclear diatomic molecules, use the dispersion function appropriatly can discribe the deformation of the atomic orbitals in the formation of molecular orbital well. But, by contrast, using the smaller basis set STO-3G can better describe the electron distribution. The work laid a foundation for the further study of the influence of overlap and the reason for Mulliken pupulation analysis based on basis sets.