共查询到17条相似文献,搜索用时 171 毫秒
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本文中用自洽总能量密度泛函集团方法研究了Ⅶ族的Ⅰ在Si(111)和Ge(111)表面的吸附。分别采用了两种集团模型来模拟顶位和三度位构型,用总能量极小原理确定了吸附的最佳构型和吸附能量,得到顶位比三度位吸附更为稳定的结果,与SEXAFS实验结果一致。本文还计算了Ⅶ族元素F,Cl,Br,I在Si(111)顶位吸附的状态密度,讨论了这系列DOS的变化情况,并与实验或其他理论结果进行了比较,最后还讨论了半经验EHT方法的适用性及限制。
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肖香珍 《原子与分子物理学报》2017,34(4):617-623
采用密度泛函理论,在slab模型下,研究了NH_x(x=1~3)在Ir(100)、Ir(111)和Ir(110)表面上的最稳定吸附位置、几何构型以及逐步脱氢分解过程,计算了相应的吸附能和活化能.计算结果表明,在Ir(100)、Ir(111)面上,NH_3是以C_3轴垂直吸附在顶位,在Ir(110)上,NH_3是以N-Ir键与表面成68.6°吸附在顶位,且吸附能依赖于表面的结构而不同,相比而言,NH_3更容易吸附在开放表面Ir(100)、Ir(110)面上,说明NH_3在这些表面的吸附具有结构敏感性.NH_(x(x=1~3))的分解,在Ir(100),NH_3的吸附与分解存在竞争,在Ir(110)面NH_3最容易分解,在Ir(111)面NH_3是分子性吸附,不能分解.NH_2、NH在三个表面均能够分解,在Ir(110)面活化能均较高. 相似文献
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应用密度泛函理论,系统研究了Al原子在Pt(111),Ir(111)和Au(111)表面的桥位、顶位、三重面心立方(fcc)洞位和六角密排(hcp)洞位这四个典型位置的吸附情况. 主要计算了三吸附体系的几何结构、平均结合能和差分电荷密度,并系统讨论了相关原子的密立根电荷布居数和投影态密度.研究发现,对于Pt(111)和Ir(111)表面,Al原子在hcp洞位最稳定,但是对于Au(111)表面,Al原子在fcc洞位最稳定.
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吸附
密度泛函理论
结合能
电子结构 相似文献
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用TB-LMTO方法研究单层的Au原子在理想的Si(100)表面的化学吸附.计算了Au原子在不同位置的吸附能,吸附体系与清洁Si(100)表面的层投影态密度, 以及电子转移情况.结果表明, Au原子在吸附面上方的A位(顶位)吸附最稳定, Au钝化Si(100)表面可以取得明显的钝化效果, 这一结论与实验事实相符合. 相似文献
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在CVD沉积SiC过程中,载气体H2与沉积SiC基体表面的反应影响沉积速率和沉积产物品质,因此研究这些微观反应机理具有十分重要的科学意义和工程价值。本文基于第一性原理研究了H2在3C-SiC(111)(硅原子暴露面)和3C-SiC(-1-1-1)(碳原子暴露面)面的吸附位置、吸附能、电子结构和覆盖率等吸附情况。发现H2倾向于吸附在3C-SiC(111)面,H原子的最稳定吸附位为OT位(顶位)且属于化学吸附。H2在吸附时会自发解离为两个H原子,以双顶位形式吸附在两个相邻的Si原子上。该过程中基体表面Si原子的电子向H偏移,此时两者的主要相互作用源于Si原子的p轨道和H的s轨道的重叠杂化。通过计算氢气在表面的覆盖率,发现吸附能随着覆盖率的增大而增大,在低H覆盖率(θH≤4/9 ML)下,H原子之间存在着较强的吸引力,随着H覆盖率的增加(θH>4/9 ML),H原子之间排斥力逐渐增大,吸附能增加趋缓,整体结构更加稳定。 相似文献
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应用EAM模型研究了氢在Ni(511)面的吸附和解离.首先计算了单个氢原子在Ni(511)面上的吸附能、吸附键长及吸附高度,发现氢在Ni(511)面上有三种相对稳定的吸附位,即台阶棱上的二重桥位B、台阶面上的三重洞位H3′以及平台面上的四重洞位H1和H2.与Ni(001)低指数面相比,明显的增加了台阶棱上的二重桥位B以及台阶面上的三重洞位H3′,并且H1位的吸附性也有所增强,说明台阶的存在影响了氢在Ni(511)表面的吸附性,使台阶附近的吸附位增多且吸附性增强;然后计算了氢分子在台阶表面上解离吸附时的活化势垒、吸附能、氢镍之间键长及氢氢之间的距离,计算结果表明台阶底部更易于使氢分子解离,台阶附近是氢吸附和解离的活性部位. 相似文献
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In the present paper the cluster model and charge self-consistent method are used to study the chemisorpti on Si(lll1), Ge(111), and GaAs(110) surfaces. The parameters in the calculations are selected to fit the respective bulk energy bands of Si, Ge, and GaAs. Some general rules of chemisorpti on Si(ll1) and Ge(ll1) are investigated and speculated. The three-fold hollow site geometry is favorable for group iii metals on Si(lll), whereas the one-fold top site is more stable for group vii elements, the reason being probably one of the favorable charge distribution. However, the situation for chemisorpti on Ge(ll1) is somewhat different. The adsorptions of group iii and v elements on GaAs(110) are also considered. The possible chemisorption geometries and the related electronic states for these systems are calculated and discussed. 相似文献
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First principles calculations of clean and adsorbate-covered surfaces of Si(001) and Ge(001) are reported. Chemical trends in the adsorption of ordered Na, K, Ge, As, Sb, S, Se and Cl overlayers are discussed. The calculations are based on the local-density approximation and employ non-local, norm-conserving pseudopotentials together with Gaussian orbital basis sets. The semi-infinite geometry of the substrate is properly taken into account by employing our scattering theoretical method. From total-energy minimization calculations we obtain optimal surface reconstructions which show asymmetric dimers for Si(001), Ge(001) and Ge:Si(001). For As:Si(001), Sb:Si(001) and Sb:Ge(001), we find symmetric adatom dimers in the equilibrium geometries. S or Se adlayers are found to be adsorbed in bridge positions forming a (1×1) unit cell with a geometry very close to the configuration of a terminated bulk lattice. Cl atoms adsorb on top of the dangling bonds of symmetric Si dimers residing in the first substrate-surface layer. Our calculations for Na:Si(001) and K:Si(001) confirm valley-bridge site adsorption for half monolayer coverage. For full monolayer alkali-metal coverage, adsorption in pedestal and valley-bridge positions is found to be energetically most favourable. The calculated optimal adsorption configurations are in excellent agreement with a whole body of recent experimental data on surface-structure determination. For these structural models, we obtain electronic surface band structures which agree very good with a wealth of data from angle-resolved photoemission spectroscopy investigations. 相似文献
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Joel A. Appelbaum G.A. Baraff D.R. Hamann H.D. Hagstrum T. Sakurai 《Surface science》1978,70(1):654-673
This paper combines a theoretical study of the Si(100) surface having a monolayer of atomic hydrogen chemisorbed to it with an experimental study of the analogous Ge(100) and Ge(110) surfaces. In the theoretical work the underlying (100) silicon surface is taken to be reconstructed according to the Schlier-Farnsworth-Levine pairing model with the hydrogen located on the unfilled tetrahedral bonds of this structure. Self-consistent calculations of the electronic potential, charge density, spectrum, and occupied surface density of states are carried out. The force on the hydrogen atoms is then calculated using the Hellman-Feynman theorem. This force is found to be close to zero, confirming that the hydrogen atoms are indeed at the equilibrium position for the chosen silicon geometry. Features in the calculated photoemission spectrum for the Si(100) 2 × 1 : H surface are discussed in terms of related features in the photoemission spectrum of Si(111) : H, but are found not to agree with the previously measured photoemission spectrum of Si(100) 2 × 1 : H. Measured photoemission and ion-neutralization spectra for Ge(100) 2 × 1 : H agree in their major features with what is calculated for Si(100) 2 × 1 : H, however, suggesting that the Ge(100) 2 × 1 : H surface is reconstricted according to the pairing model. Similarly, measured spectra for clean Ge(100) 2 × 1 agree with calculations for the row dimerized Si(100) surface. 相似文献
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The ground state of Sn/Si(111) and Sn/Ge(111) surface alpha phases is reexamined theoretically, based on ab initio calculations where correlations are approximately included through the orbital dependence of the Coulomb interaction (in the local density+Hubbard U approximation). The effect of correlations is to destabilize the vertical buckling in Sn/Ge(111) and to make the surface magnetic, with a metal-insulator transition for both systems. This signals the onset of a stable narrow gap Mott-Hubbard insulating state, in agreement with very recent experiments. Antiferromagnetic exchange is proposed to be responsible for the observed Gamma-point photoemission intensity, as well as for the partial metallization observed above 60 K in Sn/Si(111). Extrinsic metallization of Sn/Si(111) by, e.g., alkali doping, could lead to a novel 2D triangular superconducting state of this and similar surfaces. 相似文献
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J.E. Rowe 《Solid State Communications》1975,17(6):673-676
Ultraviolet photoemission spectroscopy using HeI (21.2 eV) resonance photons has been used to study cleaved Ge(111) surfaces which were also characterized by Auger electron spectroscopy and low energy electron diffraction. Higher effective resolution for both bulk and surface states was found than for recent measurements employing synchrotron radiation. 相似文献