Semiempirical Molecular Orbitals for General Polyatomic Molecules. II. One-Electron Model Prediction of the H–O–H Angle

A consistent one-electron semiempirical molecular orbital method based on the approximation Hij=Sij(2−| Sij |)(Hii+Hjj)/2has been used with atomic data to predict the equilibrium geometry of the water molecule. A variety of plausible parameters predict an equilibrium H–O–H angle in the range 95°—105°. Success and limitations of the method are attributed to the fidelity with which it reproduces important one-electron effects. In less critical cases, this model resembles the Wolfsberg—Helmholz and other non-Hückel semiempirical MO treatments.