2ND-HARMONIC GENERATION FROM MIXED-CRYSTALS OF P-NITROANILINE

Second-harmonic (SH) activities of p-nitroaniline (pNA) crystallized i n the presence of aromatic additives or impurities, have been measured by the SHG powder method with a 1064 nm Nd: YAG laser source; values were in the range 100-1000 x urea, depending on the additives and crys tal-growth conditions. The SH-active crystals showed XRD patterns subs tantially different from that of the centrosymmetric pNA crystal, and were thermally unstable. The effects of foreign substances were discus sed in terms of the control of crystal growth via an adsorption-inhibi tion mechanism.