A MODIFIED ONE-CENTER METHOD FOR MOLECULAR ELECTRONIC STRUCTURE CALCULATION: AN APPLICATION TO ${\rm H}^+_2$
A modified one-center expansion method for calculating the electronic structures of the single-electron molecule is developed. Both the radial and the angular wave functions are expanded in terms of B-splines. Using the special properties of B-splines, we build the nuclear positions into the basis functions, which makes our method approximate well the cusps of the electronic wave functions and accordingly considerably improve the convergence of eigenenergies. As a test, the five lowest σ electronic states of the [Formula: see text] molecule are calculated at the equilibrium bond length (about 2 a.u.). The energies reach an accuracy of 10-5 a.u. and partly even of 10-6 a.u. In addition, the potential applications of the present method to the electron-capture processes in ion-atom collisions are discussed.