The role of second-order perturbations in interchain interactions of one-dimensional electronic systems is examined. The general features of such interchain interactions are deduced from a simple two-chain model. From a perturbation-theoretic analysis, the second-order term originating from two different bands near the Fermi level leads to an important out-of-phase coupling of charge-density-waves on neighboring chains. The preferred distortion is predicted for various electron counts, using a

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... ransition-density analysis. Specific geometrical conclusions are derived for polyacene systems.