Ionic Clusters And Diffusion Nucleation Mechanism During The Crystallization Of Magnesium Carbonate

Anhydrous magnesium carbonate（AMC）is a new type of inorganic functional material with very high application value.Anhydrous magnesium carbonate with complete crystal form and uniform morphology has broad application prospects in many fields.In the process of solution crystallization,due to the strong combination of Mg²⁺and H₂O,it is easy to generate hydrated magnesium carbonate and basic magnesium carbonate,which affects the quality of anhydrous magnesium carbonate products.However,the current laboratory method of preparing AMC,despite the use of high energy consumption and complex operation,is still not easy to obtain high-quality AMC with uniform morphology.This situation makes us hope to find an effective regulation strategy by understanding the micro mechanisms and influencing factors of crystallization nucleation and growth process.Therefore,based on molecular dynamics simulation,this paper analyzes the influence of crystallization temperature zone,concentration and crystal surface structure on the nucleation and growth process of solution crystallization,and discusses the evolution of solute ion clusters.From the perspective of cluster movement,The idea of controlling the crystallization of anhydrous magnesium carbonate is proposed.The specific work content is as follows:Firstly,a magnesium carbonate solution-interface model molecular dynamics simulation system was established.Based on the influence of temperature on the crystallization process of ion clusters and diffusion nucleation,the physical picture of the simulation process at different temperatures was observed,and the particle diffusion in the solution was observed.The characteristics,the number and size of the clusters,the ratio of the number of solute ions forming the clusters,the evolution and distribution of the clusters,and the hydration characteristics of the clusters were statistically analyzed.Secondly,the magnesium carbonate solution-interface model system of different concentrations was established,and the influence of the concentration on the crystallization process of ion clusters and diffusion nucleation was analyzed and discussed in detail.Finally,a magnesium carbonate solution-interface model system with different crystal plane structures was established.Based on the crystal plane structure,the influence of ion clusters and diffusion nucleation in the crystallization process was analyzed and discussed in detail.The results show that the diffusion rate of solute ions interacts with cluster evolution during nucleation or grain boundary growth.Reasonable selection of temperature and concentration is not only conducive to the nucleation of clusters,but also to the grain boundary to guide the adsorption and growth of solute ions.It can also interfere with the strong binding of Mg²⁺and H₂O,which is conducive to the formation of anhydrous magnesium carbonate;（1（?）0） smooth crystal surface is more conducive to cluster nucleation and growth than （1（?）4） smooth crystal surface;in addition,a rough surface is easier to guide the growth of AMC than a smooth surface,and is conducive to dehydration.Among them,a rough surface with both kinks and steps has the best effect.