One-Center Expansion Wavefunctions for CH3−, CH4, and CH5+

Abstract

One‐center expansion (OCE) wavefunctions for the species CH₃⁻, CH₄, and CH₅⁺ are presented. These wavefunctions are expressed by configuration interaction of the singly excited states of a closed‐shell ground state. The basis set consists of STO's through l=4, belonging to the irreducible representations spanned by the σ‐bonding representation. In addition the calculations on CH₃⁻ and CH₅⁺ were done as a function of nuclear geometry. These calculations indicate that CH₃⁻ has a D_3h configuration rather than a C_3v configuration. The molecular configuration of CH₅⁺ was indicated to be D_3h rather than C_4v or C_3v. The ground‐state energies of CH₃⁻, CH₄, and CH₅⁺ were calculated to be −39.236, −39.859, and −40.036 a.u., respectively. The proton affinity of methane is calculated to be approximately 5 eV.