Density Functional Theory (DFT)

Density functional theory (DFT) was a major breakthrough because the many-particle problem was replaced by a one-electron Schrödinger equation.

This is achieved by describing the Coulomb repulsion between the electrons partly by an effective potential, the exchange-correlation potential, which depends only on the electron density. This is where the name DFT comes from.

The exact form of this potential is not known, but even simple approximations provide sufficient accuracy for many practical applications.