An improved calculation method on optical second-order susceptibilities of organic materials Original Research Article

An improved method to calculate the macroscopic second-order susceptibility of organic crystals is presented. The wave functions are obtained by the ZINDO single excited configuration interaction (ZINDO-MECI) method. The βcell tensor components for a unit cell of a crystal are calculated by the sum-over-states (SOS) method underlying the idea of “supramolecule” included the intermolecular interaction. Six organic compounds, urea, m-dinitrobenzene, 3-methyl-4-nitropyridine-1-oxide (POM), nitro-4-pyridino-2-(l)-prolinol (PNP), (N)-(4-nitrophenyl)-(l)-prolinol (NPP) and m-aminophenol have experimental macroscopic NLO coefficients, which are used as a check. A reasonable agreement is obtained between calculated nonlinear optical coefficients and experimental values. The reliability of the method is discussed in terms of the UV spectra of the compounds. The results show that the procedure developed in this article provides a new insight into the second-order susceptibilities of organic molecular crystals, which is important in molecular engineering.