What is the energy ordering of molecular orbitals in diatomic molecules of third and fourth period elements?

For diatomic molecules with less than 16 electrons, the list of molecular orbitals in order of increasing energy is:


σ1s < σ\*1s < σ2s < σ\*2s < (π2py = π2pz) < σ2px < (π\*2py = π\*2pz) < σ\*2px


From O2 onwards, because of s-p mixing, the order of energies of the molecular orbitals changes to:


σ1s < σ\*1s < σ2s < σ\*2s < σ2px < (π2py = π2pz) < (π\*2py = π\*2pz) < σ\*2px


I now want to know how the molecular orbital theory can be extended to diatomic molecules of heavier elements, such as Cl2 and Br2.


More precisely, what is the order of energies of molecular orbitals formed by the combination of atomic orbitals from the 3s, 3p, 4s, 3d and 4p subshells?


