Two-dimensional hydrogen molecule and the alternant-molecular-orbital approximation

Abstract
The eigenenergies of the hydrogen molecule are calculated in the alternant-molecular-orbital approximation. Emphasis is given to two-dimensional (2D) systems. Results for the 2D and 3D cases are compared and also with the singlet state of the variational Heitler-London approximation. Unlike what is observed in 3D, in 2D we found that in the ground-state electrons are highly correlated and that double occupancy is inhibited.