Many-body perturbation theory applied to H2

Diagrammatic many-body perturbation theory is applied to the H2 molecule using a discrete basis set composed of Gaussian orbitals. Three different zero-order potentials are tried. Corrections through third order are calculated, and higher orders are estimated. The energy obtained is accurate to about 1 kcal/mole. The technique of partial summation of certain classes of diagrams by denominator shifts is investigated. Dipole polarizabilities and transition moments are also calculated, with an accuracy of 5% or better. The use of the geometric approximation to estimate high-order corrections is discussed.