For example, the Restricted Hartree–Fock model is not able to correctly describe the dissociation curves of H2 and therefore all post HF methods that employ HF as a starting point will fail in that matter (so-called single-reference methods).
The Restricted Hartree–Fock model fails to accurately describe the dissociation curves of hydrogen gas (H2), making all subsequent methods based on Hartree–Fock as a foundation for calculations inaccurate in predicting these curves.