Interpretation of finite-field molecular cubic polarizability via real-space contributions: application to π-conjugated oligomers

A partitioning scheme for the molecular cubic polarizability γ in terms of local atomic contributions is further developed and applied to long organic conjugated molecules. We discuss, in chemically-oriented terms, the origin of the high nonresonant cubic response in polyenes and its enhancement upon push–pull substitution due to the mutual influence of the donor/acceptor substituents and the conjugated bridge. Extremely large γ values are predicted for specifically built compounds.