An extension of ab initio molecular orbital theory to nuclear motion

We propose an extension of the quantum chemical molecular orbital (MO) method to describe the nuclear motion. Both electronic and nuclear wavefunctions are simultaneously solved with the full variational MO method, by which exponents and centers of gaussian-type function (GTF) basis sets are optimized as well as the linear combination of GTF coefficients. Applications of the method to [F^-; e⁺], FH and FD systems are carried out. The calculated bond lengths and harmonic frequencies agree well with the experimental values.