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Palladium grain crystalline planes pileup calculation

Author: ZhuGuanJia
Tutor: XueDongFeng
School: Dalian University of Technology
Course: Functional Materials Chemistry and Chemical Engineering
Keywords: Crystallization Chemical bonding Pileup Morphology prediction Palladium grain Bromide ion Iodide
CLC: TB383.1
Type: Master's thesis
Year: 2011
Downloads: 31
Quote: 0
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Abstract


Crystalline field of materials science is a very common phenomenon. Nanoscience and rapid development of technology greatly expanded the scope of this research field. The morphology of the metal nanocrystals controlled study in order to obtain the desired product, still a large number of laboratories currently trying to find the optimal reactants and reaction conditions. Therefore, a deep understanding of the crystallization process and the establishment can reveal the evolution and morphology of operation to provide guidance for the synthesis of the theoretical model is necessary for the development of new materials chemistry. Crystallization process can be seen from a microscopic point of bond formation and breaking process, therefore, from a chemical point of view to describe and analyze the process will be an effective means. Based on the atomic stacking morphology stability analysis, synthesis and surface fraction of the surface atoms coordinatively unsaturated degree two factors come into bond fraction size can effectively determine the structural stability of different atomic stacking. Through the analysis of stability can be further introduced to characterize the stability of two-dimensional plane, two new parameters, thereby establishing a crystal plane relative growth rate model. Since the metal palladium is currently the most systematic experimental report found that up to morphology, morphology controllability one of the best metal nanocrystals, this article use metal palladium as a modeling example. Use the model to predict the ideal form of palladium, and the effects of nano-size effect on the morphology of the ideal. While halogen ion structure is simple, but there are obvious crystalline form regulation, therefore, we simulated bromide ions and iodide ions on palladium grain morphology. The results show that the two different ions in the crystal face of palladium adsorbed phase difference change of the surface sites of unsaturation strength and concentration, so that the bonding dynamics environment has changed. Further studies found that bromide ion to help expose the {100} plane, stable form of a cube; iodide ions, respectively, in different conditions, and contribute to the formation of octahedral rhombic dodecahedron, theoretical prediction is consistent with the experimental observations. The study also showed that some crystal plane (such as {110} surface) and the surface appearance of the relevant steps in the change of direction. This work can deepen our specific crystal surface coating agent in the evolution of the understanding of the role. Theoretical predictions and experimental observation confirms the consistency of the validity of the model, indicating that from the viewpoint of chemical bonding crystal growth is of great significance, which for crystal growth theory provides a new way.

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