elektronelektronrepulsion

Elektronelektronrepulsion, also called electron–electron repulsion, is the electrostatic repulsion between electrons, arising from their negative charge. In quantum mechanics this interaction is described by the Coulomb term in the multi-electron Hamiltonian: V_ee = (1/(4πϵ0)) ∑_{i<j} e^2 / r_ij, where r_ij is the distance between electrons i and j. This repulsion competes with the attractive force between electrons and the nucleus and influences the structure and properties of atoms and molecules.

In atoms, electron-electron repulsion partially screens the nuclear charge, reducing the effective nuclear charge experienced by outer electrons. As a result, energy levels, orbital energies, and ionization energies deviate from the hydrogenic model. Electron correlation refers to the non-independent motion of electrons caused by their mutual repulsion and is not fully captured by simple mean-field theories.

In chemistry, repulsion between electron pairs around a central atom governs molecular geometry (VSEPR theory) and affects bond strengths and angles. Spin and the indistinguishability of electrons give rise to exchange interactions, which interact with repulsion to influence bonding and magnetic properties.

Theoretical treatment of electron-electron repulsion employs methods such as the Hartree–Fock approach, which approximates a mean-field repulsion. More accurate results use post-Hartree–Fock methods (configuration interaction, perturbation theories such as MP2, coupled-cluster methods) or density functional theory, where electron-electron interaction is incorporated via exchange–correlation functionals.