Vectorial and Octupolar Components of the First-Order Hyperpolarizability in Push-Pull Benzopyranic Series

Vectorial (weight 1) and octupolar (weight 3) components of the first-order hyperpolarizability are computed using the PM3/RHF/FF method following two different decomposition schemes. These calculations evidence the importance of the weight 3 component of the tensor even in push-pull molecules. The values, output from the two decomposition schemes, are different but show the same evolutionary trend within benzopyranic molecule series. The square root of a macroscopic square average quantity ,²)^1/2 (which is usually determined in elastic second-harmonic light scattering experiment) is then computed and compared to the norm of the molecular cartesian tensor.