A novel approach to calculation of the second-order nonlinear optical susceptibilities of organic crystals based on energy-band theory

The second-order nonlinear optical susceptibilities in five organic crystals are studied based on the EHMO band-structure method. The crystals studied included m-aminophenol, urea, m-dinitrobenzene, POM [3-methyl-4-nitro-pyridine-1-oxide] and m-nitroaniline. The β(cell) tensor components for a unit cell of crystals are calculated by the sum-over-states method. Results are presented for the density of states and second-order nonlinear optical coefficients d((2))(0), which are compared with other existing calculations and experimental data. The overall agreement of our calculations with available data is quite satisfactory. Moreover, the effect of the interactions between neighboring unit cells on the hyperpolarizability tensor components of β(cell) is examined and analyzed. The results show that the procedure developed in this work provides a new insight into the second-order susceptibilities of organic molecular crystals, which is important in molecular engineering. (C) 2000 Published by Elsevier Science B.V.