Marron-weare variational computation of energy differences for motions of C2H6, B2H6, CH3CH inf2 sup+ , and CH3BH2

The passage of D_3dC₂H₆ and B2H6 toward a D₂ h bridged structure, and the motion of a methyl proton maintaining C symmetry in C₂H _inf5 ^sup+ and CH₃BH₂ are described by integral Hellmann-Feynman computations in a Frost floating spherical Gaussian basis. Marron and Weare's variational corrections to the integral Hellmann-Feynman formula forAE between statesA andB are evaluated with variational functions of the form η(ψ_A/S_AB-ψ_B)) used to refine the stateB. An analogous function ξ(ψ_B/S_AB-ψ_A) refines state A. Both η and ξ are chosen variationally to minimize Marron and Weare's functional. No obvious advantage of the variational method became apparent in this simple application.