Applications of Variational-Perturbation Theory to Molecules. I. The Water Molecule

Abstract
The energy of the ground state of the water molecule is obtained through the second order using the Rayleigh–Schrödinger variational-perturbation method. The resultant value of − 75.9935 a.u. differs from the exact nonrelativistic energy by 0.6%. The method is applicable to other hydrides.