Kinetic anomalies are oscillating nonmonotonous changes of growth rate with temperature. It was found in 1967 by V.Sipyagin and A.Chernov (Sipyagin, 1967; Sipyagin, Chernov, 1972) and now is known for dozens of water-soluble salts (Punin, Petrov, 1972; Kibalczyc, Kolasinski, 1977; Franke, 1986; Bocharov, 2004 etc). It was established that kinetic anomalies has influence on crystal morphology (Glikin et al, 2003) as well as chemical composition (Bocharov et al, 2009). So this phenomenon is important for industrial crystal growth from solution, mineralogical reconstruction and basic researches of crystal growth theory. Nevertheless this phenomenon is poorly known and not covered by monographs and articles. It is supposed that anomalies formation linked to structural transitions on molecular level (Bocharov, Glikin, 2008; Bocharov, 2011) at different parts of crystal-solution system (bulk of solution and adsorption layer). Comparison of kinetic anomalies features for different systems can give us information about anomalies nature as well as possibility to grow mixed crystals with precision control of chemical composition distribution.

From this point of view it is interesting to compare kinetic anomalies for matters with fixed chemical composition and matters with varying chemical composition (mixed crystals) as well as kinetic anomalies changes in chain of intermediate solution compositions between pure members. We investigated kinetic anomalies of mixed crystals growth for NaClO₃-NaBrO₃ system by traditional microcrystallization method and for Cu-Hg system by modified electrocrystallization method (Bocharov, Glikin, 2008). Kinetic anomalies for NaClO₃-NaBrO₃ system were investigated in temperature range 33 – 41 ^oC and compound ratio in solution which responds to alyotropic point of system (NaClO₃:NaBrO₃ = 20:1). For Cu-Hg system kinetic anomalies were investigated in temperature range 45-53 ^oC and compound ratio in solution from 1:50 to 1:500 (Cu:Hg). Extreme compound ratios correspond to pure members deposition since difference of electrochemical potentials for Cu and Hg exists.

Our investigations show that low deviation of solid phase chemical composition from end-member composition resulted in kinetic anomalies which are similar to anomalies of main phase as temperature position of peaks as well as peak intensity. As example kinetic anomalies of Na(Cl,Br)O₃ in the temperature range 33 – 41 ^oC are characterized by four maxima of growth rate. Three of these maxima correspond to maxima of pure sodium chlorate. Kinetic anomalies of Cu-amalgams deposited from solution with compound ratio 1:50 are characterized by seven maxima in the temperature range 47 – 52 ^oC. Five of them correspond to maxima of copper kinetic curve and two correspond to maxima of mercury kinetic curve. So, main difference of mixed crystal kinetic anomalies is existing additional peaks which relate to kinetic anomalies of opposite end-member. Changes in compound ratio result in complication of kinetic curves. It can be described as superposition of end-member kinetic curves plotted by maxima of growth rate.

Thus, on one hand, kinetic anomalies of mixed crystals growth are defined by initial ratio of compounds in solution. On other hand it is defined by kinetic curves of end-members. In some cases it can result in specific zone formation.

 The reported study was partially supported by Russian Foundation for Basic Research, research project No. 12-05-00876-а.

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1. Quantitative analysis of morphology of polycrystalline precipitate received in temperature ranges of growth rate anomalies
2. A new kind of zone in sodium chlorate-bromate crystal grown in areas of temperature anomalies of growth rate («kinetic anomalies»)