From Quantum-Dot Nanorings to Polyacetylene via Small Annulenes: A Full Configuration Interaction Description Based on an Extended Hubbard'Su-Schrieffer-Heeger Model

From Quantum-Dot Nanorings to Polyacetylene via Small Annulenes: A Full Configuration Interaction Description Based on an Extended Hubbard–Su-Schrieffer-Heeger Model

Quantum chemical approaches to molecules — like the annulenes (cyclic polyenes C_NH_N, where N is an integer) considered here — usually examine the impact of electron-electron interaction at frozen molecular geometries within approaches based on a single (or a few) Slater determinant(s). In the solid-state community, polyacetylene, their asymptotic limit [(CH)_∞ = lim_N→∞C_NH_N] is oftentreated as a statically dimerized chain within a single-electron picture (static Su-Schrieffer-Heeger (SSH) model). More recent studies on quantum-dot nanorings employed SSH models extended to embody quantum phonon dynamics and Hubbardtype electron-electron interaction terms, which are treated exactly within a full configuration (CI) description. In the present paper we show that this full CI extended Hubbard-SSH framework provides a unitary description of important properties both of small annulenes (cyclobutadiene, benzene, and octatetraene) and of polyacetylene based on a few N-independent model parameters. These results emphasize the importance of the full CI description; provided that a few important terms are retained, a schematic description of the interaction does not preclude a reasonable description.