HartreeFockEnergie

HartreeFockEnergie, commonly referred to as the Hartree–Fock energy, is the electronic energy obtained from the Hartree–Fock approximation in quantum chemistry. It is the expectation value of the electronic Hamiltonian with respect to a single Slater determinant built from spin-orbitals optimized in a self-consistent field procedure. This energy accounts for the average repulsion between electrons (Coulomb term) and the exchange interaction arising from the antisymmetry of the wavefunction. It does not include electron correlation beyond exchange, so the Hartree-Fock energy typically lies above the exact nonrelativistic energy for a given molecular system.

There are variants: restricted HF (RHF) for closed-shell systems, unrestricted HF (UHF) for open-shell, and restricted open-shell HF (ROHF) for certain cases. Computationally, HF energy depends on the chosen basis set and converges with larger basis sets; the calculation is carried out iteratively until the orbitals converge in the self-consistent field cycle, often with convergence acceleration such as DIIS.

Applications and limitations: HF energy provides a simple, size-extensive reference and a starting point for post-HF methods like MP2, CCSD, etc.; it neglects dynamic correlation; the difference between exact energy and HF energy is called the correlation energy. In practice, HartreeFockEnergie is a foundational quantity in quantum chemistry, used to approximate total electronic energy and to generate molecular orbitals for further refinement.