Natural Orbitals for H2

Abstract

Natural‐orbital (norb) expansion coefficients are presented for the LCAO–MO–SCF–CI wavefunction of Fraga and Ransil for separations between 1.0 and 12.0 bohrs. These results are compared in detail with those obtained by Shull and Prosser for the He₂⁺⁺ system. Judged at the two‐norb level, the norb expansion converges faster for He₂⁺⁺ than for H₂ at all internuclear separations. Otherwise, the norb coefficients for the two systems have quite similar dependence on scaled separations. The occurrence of more than one positive norb coefficient is found to be an intrinsic property of the approximate wavefunction.