Searching for new nonlinear optical materials on the basis of the anionic group theory

Based on the anionic group; theory of nonlinear optical crystals and the relationship between the microscopic nonlinear coefficients of;the anionic group and the macroscopic coefficients of the crystal, an evaluation system has been established to analyze the spatial arrangement of the anionic groups in a crystal lattice. A structural criterion is given to find which crystal has a favorable spatial arrangement of the anionic groups in terms of its nonlinear effects. Some of the currently available nonlinear optical crystals have been analyzed in this way with a computer program to test the evaluation method, and results demonstrate that the above structural criterion is quite reliable. Several compounds with crystallographic data from an inorganic crystal structure database were evaluated and found to be possible good candidates for nonlinear applications. (C) 1998 American Institute of Physics.