Local Energies, the Integral Hellmann–Feynman Method, and Partitioning the Hamiltonian

The connection between local-energy functions and the integral Hellmann–Feynman (IHF) method is discussed. Richardson and Pack's method of partitioning the Hamiltonian is related to local energies and their numerical results are rationalized. It is shown that local-energy concepts can be useful in choosing the best from among the many possible IHF calculations for a process. IHF calculations already in the literature are analyzed from this standpoint. Calculations on HeH+ are reported which indicate that the IHF method may be particularly useful for shorter one-center expansions.