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U Dahmen C J D Hetherington V Radmilovic E Johnson S Q Xiao C P Luo 《Microscopy and microanalysis》2002,8(4):247-256
Twinning plays an important role in phase transformations and can have significant effects on microstructural evolution. Different roles of twinning in the development of microstructures during precipitation and phase transformations are reviewed and illustrated with examples from investigations by high-resolution electron microscopy, including the effect of multiple twinning on the development of Ge precipitates in Al-Ge and Ag-Ge alloys, the twin dissociation of grain boundaries in Au, the formation of hexagonal Si at twin intersections and the effect of twin boundaries on the equilibrium shape of Pb inclusions in Al. 相似文献
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The influence of introducing water molecules into a cation-pi complex on the interaction between the cation and the pi system was investigated using the MP2/6-311++G method to explore how a cation-pi complex changes in terms of both its geometry and its binding strength during the hydration. The calculation on the methylammonium-benzene complex showed that the cation-pi interaction is weakened by introducing H(2)O molecules into the system. For example, the optimized interaction distance between the cation and the benzene becomes longer and longer, the transferred charge between them becomes less and less, and the cation-pi binding strength becomes weaker and weaker as the water molecule is introduced one by one. Furthermore, the introduction of the third water molecule leads to a dramatic change in both the complex geometry and the binding energy, resulting in the destruction of the cation-pi interaction. The decomposition on the binding energy shows that the influence is mostly brought out through the electrostatic and induction interactions. This study also demonstrated that the basis set superposition error, thermal energy, and zero-point vibrational energy are significant and needed to be corrected for accurately predicting the binding strength in a hydrated cation-pi complex at the MP2/6-311++G level. Therefore, the results are helpful to better understand the role of water molecules in some biological processes involving cation-pi interactions. 相似文献
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The γ(HO2) was elevated with increase of Cu(II) concentrations in aqueous (NH4)2SO4 aerosol. The threshold of Cu(II) concentration was 10-3 mol/L for the dramatic increase of γ(HO2) to 0.1, suggesting sensitive γ(HO2) value to concentration of transition metal ions in aerosol. 相似文献
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在25±0.02℃、0.025mol·dm~(-3)KCl介质及磷酸盐缓冲条件下,用光度滴定法研究了羟基-氧钼(V)[5,10,15,20-四(4-磺酸基苯基)]卟啉配合物在水溶液中的二聚平衡,用线性最小平方法确定了平衡模型,求得二聚反应平衡常数pK_el=4.34±0.28,单体的摩尔吸收εm(447um)=1.27×10~4εm(475um)=2.01×10~4;二聚体的摩尔吸收ε_d(447nm)=3.17×10~4,ε_d(475nm)=1.40×10~4。 相似文献
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