ON THE CONSTANCY OF MILLER DELTA(IJK)(2-OMEGA-OMEGA,OMEGA) COEFFICIENT IN CRYSTALS OF DIFFERENT SYMMETRIES

The relationship between Miller's delta(ijk) (2 omega; omega, omega) a nd the crystal structure is analyzed. Changes in delta(ijk) (2 omega; omega, omega) in crystals of different symmetries are compared. It is found that the prediction of second harmonic generation based on the a ssumption of rough constancy of delta(ijk) (2 omega; omega, omega) can be improved by employing different values of the averaged delta(ijk) (2 omega; omega, omega) for various crystallographic systems. The resu lts obtained show that the assumption works better for crystallographi c systems of higher symmetries.