Structural mechanism of the impurity effect on kinetics of crystal growth.Crystallochemical aspect

It has been established that metal impurities M3+ (Fe3+, Cr3+) and M2+ (Co2 +, Ni2+) have a different effect on the kinetics of face growth of potassiu m dihydrophosphate (KDP) and potassium acid phthalate (KAP) crystals, which can hardly be interpreted in terms of the existing concepts. The crystallo chemical analysis and computer modeling of the KDP structure provided the e stablishment of different mechanisms of incorporation of M2+ and M3+ impuri ties into the crystal structure: the first impurities form impurity cluster s, whereas the second impurities occupy isolated positions. This fact prede termines the different deformation of the crystal matrix caused by M2+ and M3+ ions. The allowance for this fact provided the interpretation of differ ent distribution coefficients of M2+ and M3+ impurities and their specific effect on the growth kinetics and defect concentration in KDP and KAP cryst als. (C) 2000 MAIK "Nauka/Interperiodica".