Theory of molecular optoelectronics. IX. Calculation of χ⁽²⁾ from theoretical hyperpolarizabilities for DAN

Components of the crystal quadratic susceptibility tensor χ² for second‐harmonic generation are calculated for the title compound, 4‐(N, N‐dimethylamino)‐2‐acetamido‐nitrobenzene. Input data are the crystal structure and refractive indices and CNDO hyperpolarizabilities; two different sets of refractive indices give similar results. The calculations yield effective polarizabilities as well as both rigorous and anisotropic Lorentz local electric fields. Susceptibility components are close to 10 pm V⁻¹, rather smaller than those deduced experimentally and showing a weaker dependence on direction; Kleinman symmetry is mostly observed within 10%. Screened dipoledipole interactions using CNDO dipole moments amount to −80 kJ mol⁻¹, implying permanent fields of 2 GV m⁻¹.