Method of non-paired spatial orbitals. Part 3.—Anthracene and phenanthrene

Abstract

The method of Non-Paired Spatial Orbitals (NPSO) is applied to the π-electron systems of anthracene and phenanthrene and the energies calculated using NPSO wavefunctions containing one adjustable parameter are compared with those obtained from comparable Alternant Molecular Orbital (AMO) functions. The NPSO method, even without full spin projection, is found to be considerably more effective in lowering the energy than the AMO method and therefore makes better allowance for electron correlation. For both molecules the energy for the NPSO function is minimised when the adjustable parameter is close to the value of 0.25 found for other systems.