The structure᎐polarization relationship was investigated in a series of polysulfanes, H S . The reported results demonstrate that the forms of 2 n change of the polarizability components, ␣ , and the second hyperpolarizability ii components, ␥ , as well as the average values ␣ and ␥ , respectively, of H S iiii 2 n
with n are similar. This shows that polarizability components can be easily used to determine corresponding hyperpolarizability data. A remarkable change of the hyperpolarizabilities with the molecular geometry of H S was found. This 2 n result can be used for the design of nonlinear optical materials with optimum properties. The present study uses the flexible bonded H S and is 2 n complementary to the works that considered the effect of conformational changes of -conjugated systems on their hyperpolarizabities. The present computations were performed using the semiempirical approaches MNDO and MNDOrd, as well as ab initio methods with STO-3G, extended with polarization and diffuse w x functions, and 3s2 pr7s5 p2 d sets for H S . At the ab initio level, the electronic 2 n and the vibrational contributions to polarizabilities and hyperpolarizabilities were both computed for several members of H S . The frequency dependence 2 n of the above contributions and the static limit were discussed. Electron correlation was taken into account for several test cases using MP2 theory. The selected methods and the variety of the approximations on which they rely