Size dependence of optical nonlinearity for H-capped carbon chains, H-(C≡C)n-H: Analysis of its nature and prediction for long chains

Based on the computational approach that can accurately describe their geometric structures and electronic spectra, we have theoretically studied the nonlinear optical (NLO) properties of H-capped carbon chains, H-(C≡C)n-H, for the first time. Special attention was paid to the size dependence of the molecular (hyper)polarizability of these species through nonlinear fitting of the data, which was thoroughly discussed at the electronic structure level by in-depth wavefunction analyses. The results are expected to provide theoretical guidance for the property prediction of arbitrarily long carbon chains not yet synthesized.