Ab initio studies of the static electronic first hyperpolarizability of polysilanenitrile

We have carried out a thorough study of the methodology/basis set dependences in predicting first hyperpolarizability (β) for polysilanenitrile (PSN) by using various wavefunction and density-based methods. Correlations between β and the bond length alternation values (Δr) are explained. Comparisons were made between PSN and the isoelectronic and isovalent analogues, and both the similarities and the differences in the β value behavior in these three polymers are discussed by using the resonance structure theory.