 to develop computer programs to use Slater orbitals to produce self-consistent field (SCF) molecular orbitals.The ethane barrier (see diagram at right) was first calculated accurately by Pitzer and Lipscomb using Hartree Fock Self-Consistent Field (SCF) theory.Ethane gives a classic, simple example of such a rotational barrier, the minimum energy to produce a 360-degree bond rotation of a molecular substructure.