THEORETICAL-STUDIES FOR NOVEL NONLINEAR-OPTICAL CRYSTALS

To fulfil the ''molecular engineering'' of non-linear optical crystals , two theoretical models suitable respectively for the studies of the absorption edge and birefringence of a non-linear optical crystal have been set up. Molecular quantum chemical methods have been adopted in the systematic calculations of some typical crystals. DV-SCM-X alpha m ethods have been used to calculate the absorption edge on the UV side of BBO, LBO, KB5, KDP, Na2SbF5, Ba2TiSi2O8, iodate and NaNO2 crystals. Ab initio methods have been adopted to study the birefringence of NaN O2, BBO, LiIO3 and urea crystals. All the theoretical results agreed w ell with the experimental values. The relationship between structure a nd properties has been discussed. The results will be helpful to the s earch for novel non-linear optical crystals.