ROHF
Restricted Open-Shell Hartree-Fock, often abbreviated as ROHF, is a quantum mechanical method used in computational chemistry and physics to approximate the electronic structure of molecules and atoms that have an odd number of electrons, or more generally, open-shell electronic configurations. Unlike the Restricted Hartree-Fock (RHF) method, which assumes that all electrons are paired and occupy the same spatial orbitals with opposite spins, ROHF explicitly accounts for the presence of unpaired electrons.
In ROHF, each spatial orbital is occupied by at most one electron with a specific spin (alpha
The computational cost of ROHF is comparable to RHF, making it a practical choice for many open-shell