Coupled cluster method with first‐order correlation orbitals versus multireference configuration interaction method. Accurate calculations for HF, H₂O, and NH₃

This article shows that with our Hylleras‐functional based method¹ for generating correlation orbitals, we can determine electronic structures for small polyatomic systems very accurately. The procedure is ab initio, uses conventional Gaussian basis sets, and solves the electronic Schrödinger equation with the coupled cluster method. A comparison is made with MRCI results obtained in equivalent basis sets for the HF, H₂O, and NH₃ molecules.