A Theoretical Study Of Electron Transfer Reaction Mechanism For Halogen-alkali Molecule

Accurate establishment of potential energy surface(PES)takes significant part in the study of electron transfer,which is sufficiently showed in the study of harpooning effect.Electron transfer can occur at positions where the diabatic potential energy suifaces crosses.Therefore,the premise of estimating the harpooning effect mechanism is to obtain an accurate value of crossing point(Rc).With the development of theoretical methods,the potential energy curve is constructed based on high-level methods and the increasing size of basis sets,the charge of diabatic is localized and can be obtained by a unitary transformation from the adiabatic states.As well know,the ab initio valence bond theory is able to provide a compact wave function with strictly localized orbitals to capture the nature of chemical bonding.In this dissertation,necessarily proposed computational scheme is applied to construct the diabatic states explicitly,and to evaluate electronic coupling directly for the halogen-alkali molecules which used VB function.Benefit form the chemical insight provided by VB theory,the results consist with experimental ones.In Chapter 1,we have briefly reviewed the significance of the potential energy curve in the study of electron transfer reaction,the background of the harpooning effect,and the theory of VB method related to this paper.In Chapter 2,the appreciate interpretation of the difference between the adiabatic and diabatic states was shown.In this chapter,we also have introduced the concept of the non-crossing principle and the conical intersection.Finally,based on above,the correlation between the valence bond theory and the diabatic state is discussed.It is concluded that the valence bond theory has a great advantage in constructing the diabatic state.In Chapter 3,we skillfully selected the valence bond structure to describe potential energy curves of diabatic state of LiF molecule,which balances the electron correlation energy of the ionic-F-in the ionic state and the covalent state.An accurate crossing point is obtained.We also obtained the coupling curve with the exponential decay change along the change of bond length.In summary,the diabatic states constructate in the VB way are appropriate.In Chapter 4,following the calculation method of Chapter 3,the diabatic state of other halogen-alkali molecules including LiCl,LiBr,LiI,NaF,NaCl,NaBr and NaI molecules were also studied.