Benchmark full configuration-interaction calculations on HF and NH2

Abstract
Full configuration‐interaction (FCI) calculations are performed at selected geometries for the 1∑+ state of HF and the 2 B 1 and 2 A 1 states of NH2 using both DZ and DZP Gaussian basis sets. Higher excitations become more important when the bonds are stretched and the SCF reference becomes a poorer zeroth‐order description of the wave function. The CASSCF‐MRCI procedure gives excellent agreement with the FCI potentials, especially when corrected with a multireference analog of the Davidson correction.