Nucleation,morphology, and structure of sub-nm thin ceria islands on Rh(111)

The early stages of ceria growth on Rh(111) at high temperature have been investigated by low-energy electron microscopy and photoemission electron microscopy. Ceria was deposited by reactive Ce deposition at substrate temperatures between 700°C and 900°C in an oxygen ambient of 5 × 10⁻⁷ Torr. At 700°C, we observe a high nucleation density of 100-nm-sized islands. With elevated temperature, the average island size increases, and the nucleation density decreases. Triangularly shaped islands nucleate preferentially at step edges, with seemingly abrupt interfaces between Ce and Rh. At 900°C, the island edges are still straight, but during growth the islands lose their triangular form. Instead, growth along the substrate step edges becomes favorable, leading to a maze-like morphology. Atomic force microscopy reveals islands of 0.3 to 0.6-nm height, consistent with ceria islands formed by one or two trilayers (O―Ce―O) of ceria. Moreover, the second layer of the islands is also triangularly shaped, with lateral dimensions of 50 nm and similar step heights. IV-LEEM analysis leads to the conclusion that the rhodium surface is covered by a layer of reduced cerium oxide, which is partially overgrown by smaller islands of CeO₂.     

Modeling aqueous electrolyte solutions: Part 1. Fully dissociated electrolytes

Liquid densities (pvT), vapor pressures (VLE), and mean ionic activity coefficients (MIAC) at 25 °C of 115 single-salt electrolyte solutions containing univalent up to trivalent ions are modeled with the ePC-SAFT equation of state proposed by Cameretti et al. [L.F. Cameretti, G. Sadowski, J.M. Mollerup, Ind. Eng. Chem. Res. 44 (2005) 3355–3362; ibid., 8944]. For each ion, only two model parameters were adjusted to experimental density and MIAC data. Without using any additional binary parameters, ePC-SAFT is able to reproduce experimental data of the respective salt solutions up to high electrolyte molalities. Moreover, it is even able to describe the reversed MIAC series for alkali hydroxides and fluorides.     

Cu(001)表面CO吸附单层结构和电子态的第一性原理研究

用密度泛函理论(DFT)研究了Cu(001)表面CO吸附单层的表面性质. 总能计算结果表明, 顶位结构总能最低, 相应位置的CO分子吸附能最大. 谷位吸附结构的衬底原子层间距相对于清洁表面的膨胀量约为10%, 从而导致了谷位吸附的不稳定性. 在顶位、桥位和谷位三个吸附结构中, C和Cu原子之间的距离dC-Cu分别为0.1868、0.1975和0.2231 nm, 对应的CO分子键长为0.1154、0.1165 和0.1175 nm. 计算了CO分子的态密度(DOS). 结果表明, 衬底与分子的作用主要是分子和金属轨道的杂化. 在吸附过程中, 电荷主要从碳原子的s轨道向p轨道转移. 在顶位、桥位和谷位吸附结构中, 每个碳原子内电荷的转移量分别为0.45e、0.54e 和0.55e. 衬底向吸附分子的电荷转移量不大, CO 吸附分子层为一绝缘层.     

高纯锗探测器的广泛应用和自主研制进展

以目前国际上极为活跃开展的暗物质探测、无中微子双 衰变研究为例,评述了高纯锗探测器的重要性及其广泛的应用前景。介绍了己开展的高纯锗单晶、探测器制备的关键技术研究进展:合作单位已研制出了用于高纯锗单晶材料制备的区熔炉、单晶炉;并制备出直径为20  50 cm、纯度为12N(< 41011  atoms/cm3)、位错< 5000 atoms/cm2 的锗单晶;掌握了高纯锗探测器(平面型、同轴型)制备的关键技术,用进口高纯锗单晶材料制备出的同轴型高纯锗探测器对射线的能量分辨率及探测效率均达到进口产品指标,使用自制的12N 高纯锗单晶材料己制备出平面型高纯锗探测器。呼吁加速高纯锗研制的自主创新步伐,尽早实现其国产化目标。The article reviews importance and wide applications of HPGe detector, especially the application on the dark matter search experiment and double beta decay experiment. The research progress on the Highpurity germanium single crystal and HPGe detector in China has been introduced. The cooperation partner developed new type zone-refining furnace and single crystal furnace. The ultra-purity germanium single crystal with 20~50 cm, purity up to 12N(net impurity concentration is less than 41011 atoms/cm3), and dislocation less than 5 000 /cm3 was prepared. The key technologies for preparing planar and coaxial HPGe detector were mastered. The coaxial detector, which has been made of imported ultra-purity germanium single crystal has excellent energy resolution and efficiency as the imported commercial detector. The planar detector using selfmade germanium single crystal was also successfully manufactured. The research group appeals for speeding up the pace of independent innovation on the high-purity germanium, and achieving the high-purity germanium localization as soon as possible.     

烷基锌与亚胺不对称加成反应的研究进展

综述了烷基锌与亚胺不对称加成反应的最新进展。参考文献31篇。     

手性Schiff Base-Ti(OR)4配合物催化醛的不对称硅腈化反应

设计合成了新型手性Salen-Ti(OR)₄配合物催化剂,用其催化一系列醛的不对称硅腈化反应,得到了e.e.值为22.4%～87.1%的氰醇.催化剂中抗衡离子的Lewis碱强烈地影响催化活性,但对反应的对映选择性影响很小,并探讨了其不对称催化反应机理.     

离子基碳-氧键断裂能量的研究(Ⅱ)──负离子基的键能

合成了3个系列芳香类含碳一氧键的化合物,用循环伏安法测定了相关的氧化还原电势,通过热力学循环首次估测了负离子基的碳-氧键的断裂能量(ΔH_cleav[C-O]^·-).结果表明:得到1个电子形成负离子基可以活化碳-氧键。这与具有相同结构的正离子基的情况是一致的,但其活化程度略小。相关分析表明:ΔH_cleav[C-O]^·-vs(ΔE_red[C-O]+ΔpK_a[HA])和ΔH_cleav[C-O]^·+vs.(ΔBDE-ΔE_ox[C-O])均呈线性。讨论了负离子基和正离子基及其母体化合物中键的特征,并与文献中有关的键能数据进行了比较。