Within the framework of the AMOEHF approximation for the Hubbard model, it is shown that the band gap E of an arbitrary regular alternant 1D system (polymer), having a singlet ground state, is different from zero, i.e., the ground state is a dielectric one. At least one of the three components of the energy gapthe topological, top; the geometrical, geom; or the correlation, corr (combined via the equation E = {corr2 + (top + geom))2}1/2is different from zero. Numerical results for several 1D alternant polymers with conjugated systems are given. 1994 John Wiley & Sons, Inc. Copyright 1994 John Wiley & Sons, Inc.
