Linnett's double quartet theory and localised orbitals

The correspondence between the Linnett double quartet (LDQ) theory and the centroids of charge of localised orbitals is extended to utilise Linnett's concept of formal charges, to discuss distortions from purely tetrahedral arrangements, to use restricted as well as unrestricted Hartree-Fock wave functions and, finally, to discuss a common class of closed shell molecules. The implications of this approach for the understanding of the computational non-paired spatial orbital (NPSO) method are explored.