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1.
The equilibrium structures and the electronic, spectroscopic and thermodynamic properties of small Pun (n=2-5) molecules are systematically investigated using the methods of general gradient approximation (GGA) of density functional theory (DFT). The results show that the bond length of the lowest-energy structure of Pu2 is 2.578 AA. The ground state structure of Pu3 is a triangle with D3h symmetry, whereas for Pu4, the ground state structure is a square (D4h) and the spin polarization of 16 for molecule Pu5 with square geometry (D4h) is the most stable structure. For the ground state structures, the vibrational spectra as well as thermodynamic parameters are worked out. In addition, the values for the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) along with the energy gap of all the Pu2-5 structures are presented. The relevant structural and chemical stabilities are predicted. 相似文献
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We investigate the structural, electronic and adsorption properties of one single CO molecule adsorbed on RhN (N = 2-19) clusters, using the density-functional theory in the spin-polarized generalized gradient approximation. It is found that the structural growth model of the RhN clusters transforms from double layers (N = 12-16) to three layers (N = 17-19). Three different adsorption types are the atop site adsorption for N = 6, 8, 9, 11, 12, the bridge site adsorption for N = 2-5, 7, 10, 13-15, 17 and the face adsorption for N = 16, 18, 19. The adsorption abilities of RhN clusters are related to C-O bond length, vibrational frequency, adsorption energy and the charge transfer between CO and Rh clusters as well as the electronic density of state. With the increase of Rh cluster size, the adsorption energy of CO adsorbed on RhN clusters tends to be 2.2 eV-2.3 eV, which is 0.2 eV-0.3 eV larger than the theoretical value (about 2.0 eV) of CO molecule adsorption on clean Rh (111) surface. 相似文献
4.
A density functional theory study on the adsorption of CO and O2 on Cu-terminated Cu2O (111) surface
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The adsorptions of CO and 02 molecules individually on the stoichiometric Cu-terminatcd Cu20 (111) surface are investigated by first-principles calculations on the basis of the density functional theory. The calculated results indicate that the CO molecule preferably coordinates to the Cu2 site through its C atom with an adsorption energy of-1.69 eV, whereas the 02 molecule is most stably adsorbed in a tilt type with one O atom coordinating to the Cu2 site and the other O atom coordinating to the Cul site, and has an adsorption energy of -1.97 eV. From the analysis of density of states, it is observed that Cu 3d transfers electrons to 2π orbital of the CO molecule and the highest occupied 5σ orbital of the CO molecule transfers electrons to the substrate. The sharp band of Cu 4s is delocalized when compared to that before the CO molecule adsorption, and overlaps substantially with bands of the adsorbed CO molecule. There is a broadening of the 2π orbital of the 02 molecule because of its overlapping with the Cu 3d orbital, indicating that strong 3d-2π interactions are involved in the chemisorption of the 02 molecule on the surface. 相似文献
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The equilibrium geometries, relative stabilities, and electronic properties of Ca2Sin (n = 1-11) clusters have been systematically investigated by using the density function theory at the 6-311G (d) level The optimized geometries indicate that the most stable isomers have three-dimensional structures for n = 3-11. The electronic properties of Ca2 Sin (n = 1-11) dusters axe obtained through the analysis of the natural charge population, natural electron configuration, vertical ionization potential, and vertical electron affinity. The results show that the charges in corresponding Ca2Sin clusters transfer from the Ca atoms to the Sin host. Based on the obtained lowest-energy geometries, the size dependence of cluster properties, such as averaged binding energies, fragmentation energies, second-order energy differences, HOMO- LUMO gaps and chemical hardness, are deeply discussed. 相似文献
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A density functional theory structures,stabilities, and study on size-dependent electronic properties of bimetallic MnAgm (M=Na,Li; n + m ≤ 7) clusters
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The equilibrium geometries, relative stabilities, and electronic properties of MnAgm(M=Na, Li; n + m ≤ 7) as well as pure Agn, Nan, Lin (n ≤ 7) clusters are systematically investigated by means of the density functional theory. The optimized geometries reveal that for 2 ≤ n ≤ 7, there are significant similarities in geometry among pure Agn, Nan, and Lin clusters, and the transitions from planar to three-dimensional configurations occur at n = 7, 7, and 6, respectively. In contrast, the first three-dimensional (3D) structures are observed at n + m = 5 for both NanAgm and LinAgm clusters. When n + m ≥5, a striking feature is that the trigonal bipyramid becomes the main subunit of LinAgm. Furthermore, dramatic odd-even alternative behaviours are obtained in the fragmentation energies, secondorder difference energies, highest occupied and lowest unoccupied molecular orbital energy gaps, and chemical hardness for both pure and doped clusters. The analytic results exhibit that clusters with an even electronic configuration (2, 4, 6) possess the weakest chemical reactivity and more enhanced stability. 相似文献
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Atomic Layer Deposition of Al2O3 on H-Passivated GeSi: Initial Surface Reaction Pathways with H/GeSi(100)-2 × 1
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The reaction mechanisms of Al(CH3 )3 (TMA) adsorption on H-passivated GeSi(100)-2 × 1 surface are investigated with density functional theory. The Si-Ge and Ge-Ge one-dimer cluster models are employed to represent the GeSi(100)-2 × 1 surface with different Ge compositions. For a Si-Ge dimer of a H-passivated SiGe surface, TMA adsorption on both Si-H^* and Ge-H^* sites is considered. The activation barrier of TMA with the Si-H^* site (1.2eV) is higher than that of TMA with the Ge-H^* site (0.91 eV), which indicates that the reaction proceeds more slowly on the Si-H^* site than on the Ge-H^* site. In addition, adsorption of TMA is more energetically favorable on the Ge-Ge dimer than on the Si-Ge dimer of H-passivated SiGe. 相似文献
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The structure, electronic and magnetic properties of HoSin(n= 1 - 12, 20) clusters have been widely investigated by first-principles calculation method based on density flmctional theory (DFT). From our calculation results, we find that for HoSin(n=1- 12) clusters except n = 7.10, the most stable structures are a replacement of Si atom in the corresponding pure Sin+1 clusters by Ho atom. The doping of Ho atom makes the stability of Si clusters enhance remarkably, and HoSin(n = 2, 5, 8, 11) clusters are more stable than their neighboring clusters. The magnetic moment of Ho atom in HoSin (n = 1 - 12, 20) clusters mainly comes from of electron of tto, and never quenches. 相似文献
9.
Experimental study of cross-section ratios in the collisions of Cq+ and oq+(q= 1-4) on atomic helium in strong-interaction region
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We have measured the cross-section ratios of helium induced by Cq+ and Oq+ (q=1-4) in an energy range from 20 keV/amu to 500 keV/amu, and obtained the two-dimensional spectra by employing the coincidence method combined with the MPA-3 data acquisition system. Hence, we obtain the ratios of total single-ionization cross-sections (SI, SC, SLSI, and DLSI), total double-ionization cross-sections (DI, DC, TI, SLDI, and DLDI) and cross-sections of every process (SI, SC, SLSI, DLSI, DI, DC, TI, SLDI, and DLDI), which induce the single-ionization and double-ionization, to the total cross sections respectively. The competitive relations between the reaction-channels and the experimental data law of each reaction-channel are revealed explicitly, and the qualitative explanations involved in those results are also presented accordingly. 相似文献
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Quasi-classical trajectory study of the isotope effect on the stereodynamics in the reaction H(2S) + CH(X2∏; v=o,j= 1)→ C(1D)+H2(X1∑g+)
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The isotope effect on the stereodynamic properties in the title reaction is investigated by a quasi-classical trajectory (QCT) method on the 11At potential energy surface at a collision energy of 23.06 kcal/mol. The angular distributions P(φr ), P(θr), P(θr, φr), and the polarization-dependent generalized differential cross sections are calculated, which demonstrate the observable influences on the rotational polarization of the product by the isotopic substitution of H with D. 相似文献
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利用密度泛函理论研究了Li原子修饰的C24团簇的储氢性能. Li原子在C24团簇表面的最佳结合位是五元环. Li原子与C24团簇之间的作用强于Li原子之间的相互作用, 能阻止它们在团簇表面发生聚集. 当Li原子结合到C24表面时, 它们向C原子转移电子后带正电荷. 当氢分子接近这些Li原子时, 在电场作用下发生极化, 通过静电相互作用吸附在Li原子周围. 在Li修饰的C24复合物中, 每个Li原子能吸附两到三个氢分子, 平均吸附能处于0.08到0.13 eV/H2范围内. C24Li6能吸附12个氢分子, 储氢密度达到6.8 wt%. 相似文献
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采用基于色散校正的密度泛函理论进行了第一性原理研究, 详细分析了肼(N2H4)在Ni8Fe8/Ni(111)合金表面稳定吸附构型的吸附稳定性和电子结构及成键性质. 通过比较发现, 肼分子以桥接方式吸附在表面的两个Fe原子上是最稳定的吸附构型, 其吸附能为-1.578 eV/N2H4. 同时发现, 肼分子在这一表面上吸附稳定性的趋势为: 桥位比顶位吸附更有利, 且在Fe原子上比在Ni原子上的吸附作用更强. 进一步分析了不同吸附位点上稳定吸附构型的电子结构、电荷密度转移以及电子局域化情况. 结果发现: 相同吸附位点的电子态密度图基本一致, 并且N原子的p轨道和与之相互作用的表面原子的d轨道之间存在态密度上的重叠; 吸附后电荷密度则主要从肼分子转移到表面原子之上; 在电子局域化函数切面图中也发现吸附后电子被局域到肼分子的N原子和相邻的表面原子之间. 这些电子结构的表征都充分说明肼分子与表面原子之间通过电荷转移形成了强烈的配位共价作用. 相似文献
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本文使用密度泛函理论(density functional theory, DFT)中的广义梯度近似(generalized gradient approximation, GGA)研究了经碱金属原子Li、过渡金属原子Ti和Fe原子修饰的富勒烯C18B2M(M=Li, Ti, Fe)的储氢性能. 研究发现, C18B2由于B的替代掺杂, 比C20对金属原子具有更高的结合能. 由平均吸附能分析可知: C18B2Li对H2的吸附能力较弱, C18B2Fe对H2的吸附能力过强, 而C18B2Ti对H2的平均吸附能介于0.45-0.59 eV 之间, 介于物理吸附和化学吸附之间 (0.2-0.6 eV), 因此可以实现常温下的可逆储氢. C18B2M(M=Li, Ti, Fe)能够吸附的H2数目最多分别为4, 6和4. 由储氢机理分析可知: C18B2Li主要通过碱金属离子激发的静电场来吸附H2, 而C18B2Ti和C18B2Fe主要通过金属原子与H2之间的Kubas作用来吸附H2. 由于C18B2Ti既有较大的储氢数目, 又可以实现可逆储氢, 因此有望开发成新型纳米储氢材料. 相似文献
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Quantitative XPS measurements have been performed in order to determine the absolute coverage of acetylene and ethylene adsorbed on Pt(111) showing a 2 × 2 LEED pattern. This LEED pattern has so far been attributed to a 2 × 2 superstructure with a coverage of 0.25. A quantitative evaluation of the C(1s) peak intensities for these adsorbed layers in comparison with adsorbed CO shows that the coverage is 0.5 instead of 0.25. Therefore the 2 × 2 LEED pattern should be assigned to a 2 × 1 superstructure in three domains rather than a 2 × 2 superstructure. 相似文献
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用X射线电子能谱(XPS)、热脱附谱(TDS)和紫外光电子能谱(UPS)方法研究了乙烯(C2 sub>H4)在Ru(1010)表面的吸附,在低温下(200K以下)乙稀(C2H4)可以在Ru(1010)表面上以分子状态稳定吸附,在200K以上乙烯(C2H 4)则发生了脱氢分解反应.TDS结果表明乙烯(C2H4)分 解后的主要产物为乙炔(C<
关键词:
乙烯
钌(1010)表面
吸附与分解 相似文献
17.
A.P. Hitchcock C.E. Brion 《Journal of Electron Spectroscopy and Related Phenomena》1977,10(3):317-330
Energy loss spectra of 2.5 keV electrons in the region of the carbon K-edge in C2H2, C2H4, C2H6 and C6H6 are report 相似文献
18.
Keisuke Fukutani 《Surface science》2009,603(19):2964-13046
Differences are seen in the adsorption of 1,2-di-iodobenzene, 1,3-di-iodobenzene, and 1,4-di-iodobenzene on graphite, as a function of exposure, using core level photoemission. The isomer 1,3-di-iodobenzene exhibits significant differences from 1,2-di-iodobenzene, and 1,4-di-iodobenzene in apparent sticking coefficients and core level binding energies. 1,3-Di-iodobenzene adsorb on graphite at 110 K in a strongly Stranski-Krastanov or Volmer-Weber (island) growth mode. The implication is that, even for small molecules adsorption, the adsorbate dipole in the plane of surface and the choice of isomer may matter. 相似文献
19.
F.P. Netzer J.A.D. Matthew 《Journal of Electron Spectroscopy and Related Phenomena》1979,16(3):359-370
Electron excited carbon KVV Auger spectra of CO, C2H4, C2N2 and C6H6 adsorbed on Pt(111) are compared. By estimating the effective Coulomb interaction between the final-state holes it is possible to associate some features with transitions observed in free molecule spectra, but others must involve at least one electron with energy within the conduction band of the metal. Such “cross-transitions” are associated with strong 2π* character of filled states in the presence of a core hole in molecules such as CO. 相似文献
20.
采用平面波赝势方法,利用基于从头计算的软件包,对乙烯和乙炔基在Ni(110)表面上吸附的问题进行了计算. 在低覆盖度时,孤立的乙烯分子的吸附能比密集时高,乙烯分子的C-C 轴大致沿衬底的Ni原子链方向(即沿[110]晶向),C-C轴与衬底Ni(110)表面有12°的倾斜角,乙烯分子的C—C键的键长为 0.147nm. 乙烯分子中接近顶位的C原子与衬底中距离最近的Ni原子为0.199nm. 在高覆盖度时,乙烯分子在Ni(110)表面上形成c(2×4)再构,每个表面二维元胞中有两个乙烯分子,每个乙烯分子的吸附位置与低覆盖度时相似,而C—C键长比低覆盖度时要短. 乙炔基是乙烯在Ni(110)表面上分解的产物. 关于乙炔基的计算结果表明:乙炔基的两个C原子的间距为0.131nm,比乙烯分子中C原子的间距更短. 与乙烯分子相比,乙炔基的吸附位置更靠近顶位. H原子与吸附在顶位上的C原子相连接,C—H键也大致沿衬底的Ni原子链方向,与Ni表面呈45°的倾斜角.
关键词:
乙烯和乙炔基
平面波赝势方法
吸附几何结构 相似文献