Effective valence bond hamiltonian for the cations of conjugated hydrocarbons

✍ Scribed by Xavier Gadea; Daniel Maynau; Jean-Paul Malrieu

• Publisher: John Wiley and Sons
• Year: 1984
• Tongue: English
• Weight: 773 KB
• Volume: 26
• Category: Article
• ISSN: 0020-7608
• DOI: 10.1002/qua.560260102

✦ Synopsis

Abstract

Previous papers have developed magnetic effective valence bond (EVB) Hamiltonians for the neutral states of π systems; following the same philosophy and using either the quasidegenerate perturbation theory or wave operator formalism, other EVB^+^ Hamiltonians may be derived for the lowest states of positively charged conjugated hydrocarbons. Their effective operators introduce both charge delocalization (which plays a much more direct role than for the neutral molecules) and effective spin ordering effects. The transferability and efficiency of this EVB^+^ Hamiltonian are tested by comparison with the exact solutions of the full PPP Hamiltonians. The resulting spectrum is much more dense than in the Koopmans' description; non‐Koopmans' states are identified for a few molecules. The applicability of the model to the d bands of metals is discussed in terms of the β/U ratio.