Are natural orbitals useful for generating an efficient expansion of the wave function?

Klaas J. H. Giesbertz

We investigate whether the natural orbitals (NOs) minimize $\Vert \Psi -\Phi {\Vert }^2$, where $\Psi$ is a wave function and $\Phi$ is a full configuration interaction (CI) approximation to $\Psi$…