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A1:Ag+ color center at the low coordination (100) and (110) surface sites of KCl and KBr thin films play an important role in providing
tunable laser oscillation and adsorbatesubstrate interactions. Double-well potentials at this site are investigated using
ab initio molecular electronic structure calculations. The calculated Stokes shifted (optical transition bands), opticaloptical
conversion efficiencies, the probability of orientational destruction, exciton (energy) transfer and Glasner-Tompkins empirical
rule suggest that laser light generation is sensitive to (i) the lattice anion, (ii) the coordination number of surface ions,
and (iii) the choice of the basis set centered on the anion vacancy. The adsorbate-substrate interactions were found to be
dependent on the electronegativity of the adatom and on the lattice anion. Optimised geometries and the coadsorption of CO
and (F, Cl, Br, I) on KCl and KBr (100) crystals are presented. Calculated chemisorption energies for CO on the (halogen atom/defect
free sites of KCl and KBr (100) crystals) showed that the coadsorption of halogen atom tends to block other adsorbate-substrate
interactions at the nearest neighbour sites. Thus if halogen atom coverage increases, the CO prefers to be adsorbed on the
K+ site of the KCl and KBr (100) surfaces and on KBr relative to KCl.
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The dissociation mechanism of a water molecule at an oxygen vacancy on the MgO(100) surface was studied by using the embedded cluster method at the DFT/B3 LYP level, while the energetic information was refined by using the IMOMO method at the CCSD level. We found that a water molecule initially adsorbs on one of the magnesium ions surrounding the vacancy site with a binding energy of 15.98 kcal mol(-1). It then can dissociate on the MgO(100) surface along two possible dissociation pathways. One pathway produces a hydroxyl group bonded to the original magnesium with a proton filling the vacancy via a transition state with a barrier of 4.67 kcal mol(-1) relative to the adsorbed water configuration. The other pathway yields two hydroxy groups; the hydroxy group originally belonging to the water molecule fills the vacancy, while the hydrogen atom binds with the surface oxygen to form the other hydroxy group. Hydrogen atoms of these hydroxy groups can recombine to form a hydrogen molecule and the surface is healed. Although the barrier (14.09 kcal mol(-1)) of the rate-controlling step of the latter pathway is higher than that of the former one, the energies of all of its stationary points are lower than that of the separated reactants (H(2)O+cluster). The effects of water coadsorption are modeled by placing an additional water molecule near the active center, which suggests that the more coadsorbed water molecules further stabilize the hydroxy species and prevent the hydrogen molecule formation through the latter pathway. The results support the photoemission spectral evidence of water dissociation on the defective MgO(100) surface at low water coverage. 相似文献
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We present the results of a density functional calculation on adsorption of O2, CO, and their coadsorption at various sites of neutral, cationic, and anionic Pd4 clusters. For all the clusters, the dissociative adsorption of oxygen sitting on Pd bridge sites is found to be preferable. Both O2 and CO binding energies are found to be higher for the anionic Pd4 cluster followed by cationic and neutral cluster. However, binding energies of O2 or CO in the coadsorption complexes follow the trend: anionic > neutral > cationic. © 2010 Wiley Periodicals, Inc. J Comput Chem, 2010 相似文献
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Adsorption and coadsorption of NH3 and NO on alumina-supported mixed copper-manganese oxide catalysts prepared from formate precursors by calcination at 670
K were studied by means of in situ FTIR spectroscopy.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
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采用固体镶嵌势能模型和DFT/B3LYP方法研究了在Pd/MgO和Cu/MgO表面吸附CO和O2分子的电子性质. 计算结果表明, 在完美MgO(100)表面Pd原子对CO和O2的吸附能分别为206.5和84.8 kJ/mol, 因此可知Pd原子更容易吸附CO分子; 而当Pd原子附着于有氧缺陷的MgO表面时, 它对两种分子的吸附都非常弱. 相反, 附着于MgO表面的Cu原子对O2分子的吸附更为有利, 其吸附能在140~155 kJ/mol之间. 研究结果还表明, 对于双分子吸附体系, 即CO+CO, CO+O2, O2+O2体系, 双分子之间的结合力可减小完美MgO表面上Pd原子与被吸附分子的相互作用, 使吸附能减少了46~96 kJ/mol. 而对于在MgO表面上的Cu原子, 只有O2+O2 体系使吸附能减少了大约50~71 kJ/mol. 相似文献
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本文应用时间分辨表面增强拉曼光谱(TRSERS)结合电位阶跃和电位扫描的方法,研究了硫脲和ClO-4在Ag电极表面的共吸附层结构。结果表明SERS谱峰强度随电极电位的响应速率与电位阶跃扫描的方向有关,TU和ClO-4在Ag表面的共吸附层在不同的电位下存在两种不同的构型,并且两种构型之间转化的难易程度不同。 相似文献
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Shixue Liu Takayoshi Ishimoto Michihisa Koyama 《International journal of quantum chemistry》2015,115(22):1597-1605
The OH? and OH adsorption structures on Au55 and Au13 nanoparticles surfaces are analyzed using density functional theory. The most stable OH? adsorption site of Au55 and Au13 nanoparticles is found to be the vertex top site followed by the (111)‐(100) edge bridge site. On the contrary, the stability order of OH adsorption is opposite to that of OH?. The adsorption of OH? is calculated to be weaker than that of OH, which shows different charge transfer and interactions with gold surface. Coadsorption on nanoparticles is studied to find that multiple OH? species prefer the most stable sites of single OH? adsorption. The hydrogen bonding between adsorbed OH? on gold surface is a key factor in stabilizing the adsorbates on the Au surface. © 2015 Wiley Periodicals, Inc. 相似文献