Hartree Fock
Hartree Fock method is an approximative resolution of the Schrödinger equation which is based on using the variational principle in which the wavefunction is written as a Slater determinant.
Indeed, a trial set of molecular orbitals is used to form a guess wave function and this improved in each consecutive iteration using the gradient of the energy with a respect to a change in the orbitals, and this until the input orbitals are the same as the output orbitals to some predefined degree of accuracy.