MS Simulation On The Mechanism Of Cerium Carbonate Growth Regulated By Polyvinylpyrrolidone

The simulation method has been widely used in many fields such as chemical industry,medicine,biotechnology and material science and technology because of its advantages of simple operation,intuitive results and macroscopical transformation.In this paper,the mechanism of template polyvinylpyrrolidone?PVP?regulating the synthesis of flower-like cerium carbonate was studied by simulation and experiment.The process of regulation was divided into three stages:induction nucleation stage,crystal growth stage and aging accumulation stage.The results are as follows:In the induction nucleation stage,infrared analysis showed that ketones in PVP bind to Ce³⁺,which led to the nucleation of cerium carbonate at the binding site.By simulating the molecular structure of PVP,the optimum spatial conformation of the molecule is found,which is isotactic angle-60°.When Ce³⁺was added,keto-oxygen in PVP combined with Ce³⁺to provide an inductive nucleation site for cerium carbonate.With the addition of carbonate,the ability of carbonate to bind Ce³⁺gradually increased.When the binding force was greater than that of PVP and Ce³⁺,cerium carbonate began to nucleate and grow at the binding position of PVP and Ce³⁺.At the crystal growth stage,cerium carbonate samples at different growth stages were characterized.The results showed that in the initial stage of reaction,cerium carbonate was less affected by PVP,and PVP had not yet played a regulatory role.Cerium carbonate grew rapidly along the normal direction of?040?crystal plane,?240?crystal plane grew slowly,and cerium carbonate grew into a narrow spindle shape.With the reaction proceeding,PVP adsorbed on the surface of cerium carbonate crystal.The growth rate of?002?and?040?crystal planes is basically unchanged,so that the crystal planes of?002?and?040?cerium carbonate gradually increase,and?240?crystal planes gradually shrink,and finally cerium carbonate grows into hexagonal flakes.MS simulation results show that the distance between ketones and Ce³⁺on cerium carbonate?002?,?040?and?240?crystal surfaces conforms to the geometric matching conditions.The growth orientation and morphology of cerium carbonate are controlled by PVP adsorption on the surface of cerium carbonate crystal.In the aging and accumulation stage,the interaction between PVP and cerium carbonate crystal planes in water environment was simulated by MS,and the mechanism of controlling the morphology of cerium carbonate by PVP was explained from the point of view of energy.At the beginning of the reaction,cerium carbonate?040?crystal plane had the highest energy,and the crystal grew along?040?crystal plane normal direction,and the growth rate of?240?crystal plane was slower,and finally retained.Comprehensive energy analysis shows that?002?the crystal surface can adsorb a large number of PVP molecules.With the growth of cerium carbonate crystals,the PVP molecules continue to twist and bend.Under the pull and winding of the PVP molecules,cerium carbonate gradually approaches each other and finally accumulates into flower shape.