Power series expansions of quantum-mechanical potential surfaces

Power series expansions of quantum-mechanical potential surfaces for H₂O and LiH₂ are generated using conventional valence displacement coordinates and alternative distance (r-r _e)/r] and angle (sin (θ/2) — sin (θ_e/2))/sin (θ_e/2)] variables. Power series in the new variables are demonstrated to be superior in terms of the quality of the fit to the energygeometry data, predicted equilibrium geometry and energy, and stability of expansion coefficients.