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选择了Amb-er99SB、CHARMM27、ENCADS、GROMOS-53A6和OPLSAA/L五种力场,并以BHandHLYP/6-311++G**优化后的气象氨基酸构型与能量作为参考标准. 研究了中性、质子化、去质子化和带帽氨基酸在不同力场下的表现. 比较了构型相对能量、顺反式结构能量差、氢键数目与强度和优化所得构型质量等代表性结果. AMBER99SB、CHARMM27和OPLSAA/L比较GROMOS53A6和ENCADS力场更为适用于气相氨基酸. 对一般性气象氨基酸和小肽分子,最推荐的力场是CHARMM27,其次为OPLSAA/L.  相似文献
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Imaging the doping elements is critical for understanding the photocatalytic activity of doped TiO2 thin film. But it is still a challenge to characterize the interactions between the dopants and the TiO2 lattice at the atomic level. Here, we use high angle annular dark-field/annular bright-field scanning transmission electron microscope (HAADF/ABF-STEM) combined with electron energy loss spectroscopy (EELS) to directly image the individual Cr atoms doped in anatase TiO2(001) thin film from [100] direction. The Cr dopants, which are clearly imaged through the atomic-resolution EELS mappings while can not be seen by HADDF/ABF-STEM, occupy both the substitutional sites of Ti atoms and the interstitial sites of TiO2 matrix. Most of them preferentially locate at the substitutional sites of Ti atoms. These results provide the direct evidence for the doping structure of Cr-doped A-TiO2 thin film at the atomic level and also prove the EELS mapping is an excellent technique for characterizing the doped materials.  相似文献
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采用基于量子力学的分子动力学方法,模拟了高能粒子辐照导致钨表面的溅射和结构损伤.结果显示,当PKA能量高于200 eV且入射角度大于65°时开始产生溅射原子,当入射角度在45°-65°之间时,钨表面因受辐照而导致的空位数目最少.因此,当PKA入射角度取在45°-65°之间时,可以有效地降低辐照导致的钨表面的结构损伤.还发现钨表面含有间隙原子时会加剧表面原子溅射,而包含空位原子且PKA取在空位附近时则会抑制表面原子的溅射.  相似文献
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A multiphysics model for a production scale planar solid oxide fuel cell (SOFC) stack is important for the SOFC technology, but usually requires an unpractical amount of computing resource. The major cause for the huge computing resource requirement is identified as the need to solve the cathode O2 transport and the associated electrochemistry. To overcome the technical obstacle, an analytical model for solving the O2 transport and its coupling with the electrochemistry is derived. The analytical model is used to greatly reduce the numerical mesh complexity of a multiphysics model. Numerical test shows that the analytical approximation is highly accurate and stable. A multiphysics numerical modeling tool taking advantage of the analytical solution is then developed through Fluent®. The numerical efficiency and stability of this modeling tool are further demonstrated by simulating a 30-cell stack with a production scale cell size. Detailed information about the stack performance is revealed and brie y discussed. The multiphysics modeling tool can be used to guide the stack design and select the operating parameters.  相似文献
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Two-dimensional transition metal dichalcogenides heterostructures have stimulated wide interest not only for the fundamental research,but also for the application of next generation electronic and optoelectronic devices.Herein,we report a successful two-step chemical vapor deposition strategy to construct vertically stacked van der Waals epitaxial In2Se3/MoSe2 heterostructures.Transmission electron microscopy characterization reveals clearly that the In2Se3 has well-aligned lattice orientation with the substrate of monolayer MoSe2.Due to the interaction between the In2Se3 and MoSe2 layers,the heterostructure shows the quenching and red-shift of photoluminescence.Moreover,the current rectification behavior and photovoltaic effect can be observed from the heterostructure,which is attributed to the unique band structure alignment of the heterostructure,and is further confirmed by Kevin probe force microscopy measurement.The synthesis approach via van der Waals epitaxy in this work can expand the way to fabricate a variety of two-dimensional heterostructures for potential applications in electronic and optoelectronic devices.  相似文献
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Oxygen vacancy (Ov) has significant influence on physical and chemical properties of TiO2 systems,especially on surface catalytic processes.In this work,we investigate the effects of O v on the adsorption of formaldehyde (HCHO) on TiO2(110) surfaces through firstprinciples calculations.With the existence of Ov,we find the spatial distribution of surface excess charge can change the relative stability of various adsorption configurations.In this case,the bidentate adsorption at five-coordinated Ti (Ti5c) can be less stable than the monodentate adsorption.And HCHO adsorbed in Ov becomes the most stable structure.These results are in good agreement with experimental observations,which reconcile the long-standing deviation between the theoretical prediction and experimental results.This work brings insights into how the excess charge affects the molecule adsorption on metal oxide surface.  相似文献
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Silicene takes precedence over graphene due to its buckling type structure and strong spin orbit coupling. Motivated by these properties, we study the silicene bilayer in the presence of applied perpendicular electric field and intrinsic spin orbit coupling to probe as quantum spin/valley Hall effect. Using analytical approach, we calculate the spin Chern-number of bilayer silicene and then compare it with monolayer silicene. We reveal that bilayer silicene hosts double spin Chern-number as compared to single layer silicene and therefore accordingly has twice as many edge states in contrast to single layer silicene. In addition, we investigate the combined effect of intrinsic spin orbit coupling and the external electric field, we find that bilayer silicene, likewise single layer silicene, goes through a phase transitions from a quantum spin Hall state to a quantum valley Hall state when the strength of the applied electric field exceeds the intrinsic spin orbit coupling strength. We believe that the results and outcomes obtained for bilayer silicene are experimentally more accessible as compared to bilayer graphene, because of strong SO coupling in bilayer silicene.  相似文献
8.
王乃舟  石孟竹  雷彬  陈仙辉 《物理学报》2018,67(20):207408-207408
自从2008年铁基超导体发现以来,人们探索并发现了一系列的铁基高温超导材料,其中FeSe基超导体因其具有的独特性质而引起了人们的广泛关注.本文主要介绍了两类新的铁基超导体,即水热合成法合成的(Li,Fe)OHFeSe及电化学插层方法合成的(CTA)xFeSe的晶体结构及超导性质;对近年发展起来的利用电双层场效应晶体管技术以及固态离子导体调控FeSe的电子态性质的研究做了简要介绍.  相似文献
9.
In order to clarify the site occupancy of rare-earth ions in rare-earth doped perovskite materials, the un-doped pure CaTiO3 and Eu3+-doped CaTiO3 samples with a series of Ca/Ti ratio were synthesized via high-temperature solid-state reaction method. X-ray diffraction (XRD) powder patterns confirm that the crystal structure keeps invariant at various Ca/Ti ratios. Measurement results of unit-cell parameters and X-ray photoelectron spectroscopy (XPS) indicate that Eu3+ ions enter into the Ca2+ site. The high-resolution photoluminescence spectra of Eu3+ ions at 20 K in all samples did not witness a significant change under the excitation at different wavelength, implying that Eu3+ ions occupy only one type of site. Considering the small spectral splitting range of 5D0 → 7F2 transition and the large intensity ratio of 5D0 → 7F2/5D0 → 7F1, it can be concluded that Eu3+ occupies Ca2+ site with larger coordinate numbers rather than Ti4+ site.  相似文献
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建立了相关实验电池多物理场模型,该模型包括了电化学反应的电化学势平衡方程、甲烷水汽重整的通用速率方程和描述阳极复杂组分气体输运的菲克定律形式尘气模型. 该理论模型的电流~电压 曲线与实验数据很好地吻合,验证了理论模型的有效性. 理论分析发现,低水汽含量甲烷重整反应中水汽的反应级数为1. 理论模型的数值仿真计算还给出多个物理量的详细信息. 据此对碳沉积机制进行深入分析,清楚地描述了工作电流对抑制焦炭生成的机制. 分析比较了积碳活性的两个表达式,发现它们都可以正确地定性反映积碳活性变化趋势,但定量数值并不确切;阳极扩散层降低积碳临界电流的机制也获得了解释. 值得指出的是,虽然积碳活性模型只是定性正确,但分析表明积碳临界电流的降低却可以通过积碳活性模型进行定量解释.  相似文献
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