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1.
运用第一性原理方法对H2分子在Ti掺杂和纯的Al(110)表面的吸附情况进行了研究,发现有Ti原子掺杂时,存在一个H2分子的吸附路径,即位于Al(110)面顶位Ti原子上方的H2分子会发生解离,并与Ti原子形成TiH2分子,然后TiH2分子向能量更低的空位移动并接近Al(110)表面.态密度与电荷布居分析显示,吸附完成后H原子与表面Al原子存在较强的共价键作用,这为Al-H类物质及Na3
关键词:
钛
吸附
解离能
第一性原理 相似文献
2.
采用了第一性原理研究了H2S在Cr(111)面的吸附解离过程,利用吸附能、吸附构型和偏态密度图(PDOS)研究了H2S及其解离产物在Cr(111)面上的吸附情况,都偏向倾斜吸附在Cr(111)面.同时研究了HS/H和S/H共吸附情况,得到共吸附物质在Cr(111)面上有明显的相互作用.最后使用线性同步和二次同步变换方法确定了解离反应的过渡态,了解到第一、二步解离的活化能分别为1.65 eV、0.82 eV,H2S分子在Cr(111)面上的解离过程是放热反应,反应能为-2.90 eV. 相似文献
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为了探求过渡金属催化剂对催化合成储氢材料NaAlH4效果的影响, 本文采用第一性原理方法研究了多种金属原子取代Al (111)表面铝原子形成的合金表面对氢的催化分解的影响. 计算结果表明, Sc, V, Fe, Ti原子掺杂的表面对氢分子分解具有催化作用. H2在对应的掺杂表面催化分解所需要的活化能分别为0.54 eV, 0.29 eV, 0.51 eV, 0.12 eV. H原子在Sc, V, Ti掺杂表面扩散需要的活化能分别为0.51 eV, 0.66 eV, 0.57 eV. 同时, 过渡金属掺杂在Al表面时倾向于分散分布, 增加掺杂表面的掺杂原子个数, 掺杂表面的催化效果体现为单个掺杂过渡金属原子的催化效果. 本研究将为金属掺杂Al (111)表面催化加氢合成NaAlH4提供理论参考. 相似文献
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采用第一性原理研究了H2O分子在Fe(100),Fe(110),Fe(111)三个高对称晶面上的表面吸附.结果表明,H2O分子在三个晶面上的最稳定结构皆为平行于基底表面的顶位吸附结构.H2O分子与三个晶面相互作用的吸附能及几何结构计算结果表明H2O分子与三个晶面的相互作用程度不同,H2O分子与Fe(111)晶面的相互作用最强,其次是Fe(100),相互作用最弱的是Fe(110)表面,而这与晶面原子的排列密度相关.吸附体系的电子结构计算结果也得出了相似的结论.同时电荷布居分析表明,H2O分子与Fe表面相互作用时,O原子与基底原子之间的电荷交换使基底Fe原子表面带负电,导致表面电位降低,也促使Fe表面更易于发生电化学腐蚀反应. 相似文献
7.
采用第一性原理研究了H2O分子在Fe(100),Fe(110),Fe(111)三个高对称晶面上的表面吸附.结果表明,H2O分子在三个晶面上的最稳定结构皆为平行于基底表面的顶位吸附结构.H2O分子与三个晶面相互作用的吸附能及几何结构计算结果表明H2O分子与三个晶面的相互作用程度不同,H2O分子与Fe(111)晶面的相互作用最强,其次是Fe(100),相互作用最弱的是Fe(110)表面,而这与晶面原子
关键词:
第一性原理
Fe单晶表面
2O分子')" href="#">H2O分子
分子吸附 相似文献
8.
采用基于密度泛函理论的第一性原理方法, 系统研究了Ni原子在钇稳定的氧化锆(YSZ)(111)和富氧的YSZ(YSZ+O)(111)表面不同位置的吸附, 以及CO和O2分子在Ni1(单个镍原子)/YSZ和Ni1/YSZ+O表面吸附的几何与电子结构特征. 结果表明: 1) 单个Ni原子倾向于吸附在O原子周围, 几乎不吸附在Y原子周围, 且Ni原子在氧空位上吸附最稳定; 2)和YSZ相比, 单个Ni原子在YSZ+O表面易发生氧化现象, Ni原子失去1.06 e电子, 被氧化成了Ni+, 吸附能力更强; 3)被氧化的Ni催化活性大幅下降, 大大减弱了表面对O2和CO等燃料气体的吸附作用. 相似文献
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采用广义梯度密度泛函理论的改进Perdew-Burke-Ernzerh方法结合周期性层晶模型,研究了CO2分子在Pu(100)面上的吸附和解离.吸附能和几何构型的计算表明,CO2以穴位C4O4构型吸附最为有利,吸附能为1.48 eV.布居分析和态密度分析表明,CO2与Pu表面相互作用的本质主要是CO2分子的杂化轨道2πμ与Pu5f,Pu6d,Pu7s轨道通过强电子转移和弱重叠杂化的方式相互作用而生成了新的化学键.计算的CO2→CO+O解离能垒为0.66 eV,解离吸附能为2.65 eV, 表明在一定热激活条件下CO2分子倾向于发生解离性吸附.O2,H2,CO和CO2在Pu (100)面吸附的比较分析表明,较低温度下的吸附强度顺序依次为O2,CO,CO2,H2;较高温度下的吸附强度顺序依次为O2,CO2,CO,H2.
关键词:
密度泛函理论
Pu (100)
2')" href="#">CO2
吸附和解离 相似文献
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The adsorption of H2O on Al(111) has been studied by ESDIAD (electron stimulated desorption ion angular distributions), LEED (low energy electron diffraction), AES (Auger electron spectroscopy) and thermal desorption in the temperature range 80–700 K. At 80 K, H2O is adsorbed predominantly in molecular form, and the ESDIAD patterns indicate that bonding occurs through the O atom, with the molecular axis tilted away from the surface normal. Some of the H2O adsorbed at 80 K on clean Al(111) can be desorbed in molecular form, but a considerable fraction dissociates upon heating into OHads and hydrogen, which leaves the surface as H2. Following adsorption of H2O onto oxygen-precovered Al(111), additional OHads is formed upon heating (perhaps via a hydrogen abstraction reaction), and H2 desorbs at temperatures considerably higher than that seen for H2O on clean Al(111). The general behavior of H2O adsorption on clean and oxygen-precovered Al(111) (θO ? monolayer) is rather similar at low temperature, but much higher reactivity for dissociative adsorption of H2O to form OH adsis noted on the oxygen-dosed surface around room temperature. 相似文献
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《Surface science》1986,172(2):349-362
Thermal desorption spectroscopy and LEED have been used to investigate the interaction of CO and hydrogen with a Pd0.75Cu0.25(111) single crystal surface with surface composition of about Pd0.7Cu0.3. The main objective was to make a comparison with the previously studied Pd0.67Ag0.33(111) (surface composition Pd0.1Ag0.9) and Pd(111) surfaces. In addition, the effect of preadsorbed H on subsequent CO dosage and the effect of adsorbed CO on postdosed hydrogen are described. Marked differences were found in the adsorption behaviour of the three surfaces towards CO and hydrogen. The maximum amount of H and CO that can be adsorbed at 250 K and pressures below 10−9 mbar is much lower on the PdCu surface than expected on the basis of the surface composition. This effect appears to be caused by a low heat of adsorption of hydrogen and CO and Pd singlet sites. Arguments are presented that singlet Pd sites or isolated Pd atoms in a Cu or Ag matrix are able to trap and dissociate the hydrogen molecule at 250 K. The CO desorption spectra are not influenced by pre- or postexposed hydrogen. Adsorbed CO hampers the uptake of hydrogen upon subsequent exposure to hydrogen. Postdosed CO causes adsorbed H adatoms to move to the bulk (adsorbed H). CO exposure at 250 K results in a very broad desorption plateau between 310 and 425 K with hardly discernable maxima. The results can be explained in terms of the size and relative concentration of the various Pd sites present on the surface (triplet, doublet and singlet sites). It can be concluded that for Pd (111) the heat of adsorption of both CO and H differ appreciably for the triplet, doublet and singlet sites. The effect of site has a larger contribution to the decrease of the heat of adsorption with coverage than the effect of lateral interaction in the adlayer. For Pd(111), PdCu(111) and PdAg(111) the effect of the available Pd sites is the major effect that determines the heat of adsorption, followed by the effect of lateral interaction and for the alloy surfaces the electronic or ligand effect. 相似文献
13.
Brett A. Sexton 《Surface science》1981,102(1):271-281
The interaction of methanol with clean and oxygen-covered Pt(111) surfaces has been examined with high resolution electron loss spectroscopy (EELS) and thermal desorption spectroscopy (TDS). On the clean Pt(111) surface, methanol dehydrogenated above 140 K to form adsorbed carbon monoxide and hydrogen. On a Pt(111)-p(2 × 2)O surface, methanol formed a methoxy species (CH3O) and adsorbed water. The methoxy species was unstable above 170 K and decomposed to form adsorbed CO and hydrogen. Above room temperature, hydrogen and carbon monoxide desorbed near 360 and 470 K, respectively. The instability of methanol and methoxy groups on the Pt surface is in agreement with the dehydrogenation reaction observed on W, Ru, Pd and Ni surfaces at low pressures. This is in contrast with the higher stability of methoxy groups on silver and copper surfaces, where decomposition to formaldehyde and hydrogen occurs. The hypothesis is proposed that metals with low heats of adsorption of CO and H2 (Ag, Cu) may selectively form formaldehyde via the methoxy intermediate, whereas other metals with high CO and H2 chemisorption heats rapidly dehydrogenate methoxy species below room temperature. 相似文献
14.
We investigate the adsorptions of Ar on Al (111) and Ir (111) surfaces at the four high symmetry sites, i.e., top, bridge, fcc- and hcp-hollow sites at the coverage of 0.25 monolayer (ML) using the density functional theory within the generalized gradient approximation of Perdew, Burke and Ernzerhof functions. The geometric structures, the binding energies, the electronic properties of argon atoms adsorbed on Al (111) and Ir (111) surfaces, the difference in electron density between on the Al (111) surface and on the Ir (111) surface and the total density of states are calculated. Our studies indicate that the most stable adsorption site of Ar on the Al (111) surface is found to be the fcc-hollow site for the (2 × 2) structure. The corresponding binding energy of an argon atom at this site is 0.538 eV/Ar atom at a coverage of 0.25 ML. For the Ar adsorption on Ir (111) surface at the same coverage, the most favourable site is the hcp-hollow site, with a corresponding binding energy of 0.493 eV. The total density of states (TDOS) is analysed for Ar adsorption on Al (111) surface and it is concluded that the adsorption behaviour is dominated by the interaction between 3s, 3p orbits of Ar atom and the 3p orbit of the base Al metal and the formation of sp hybrid orbital. For Ar adsorption on Ir (111) surface, the conclusion is that the main interaction in the process of Ar adsorption on Ir (111) surface comes from the 3s and 3p orbits of argon atom and 5d orbit of Ir atom. 相似文献
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《Surface science》1986,172(3):733-753
The adsorption and decomposition of acetic acid on Al(111) have been studied using electron energy loss spectroscopy (EELS), temperature programmed desorption (TPD), and Auger electron spectroscopy (AES). Acetic acid reacts with clean Al(111) at 120 K to form a surface acetate species. The adsorbed acetate bonds to the surface in a symmetric configuration with Cs symmetry at 120 K. The adsorption of molecular acetic acid occurs at this temperature only after saturation of the surface acetate layer; this physisorbed multilayer desorbs molecularly at 167 K. Thermal decomposition of the adsorbed acetate leads to a carbon- and oxygen-covered surface; the only detectable thermal decomposition product is H2. Electron irradiation induces a similar decomposition process of the surface acetate. 相似文献
17.
High resolution electron energy loss spectroscopy has been applied to study the adsorption of benzene (C6H6 and C6D6) on Pt(111) and Ni(111) single crystal surfaces between 140 and 320 K. The vibrational spectra provide evidence that benzene is chemisorbed with its ring parallel to the surface, predominantly π bonded to the platinum and nickel surface respectively. A significant frequency increase of the CH-out-of-plane bending mode, largest in the case of platinum, is observed compared to the free molecule. On both metals two phases of benzene exist simultaneously, characterized by a different frequency shift. The shifts are explained by electronic interaction between the metal d-orbitals and molecules adsorbed in on top and threefold hollow sites respectively. The vibrational spectra of the multilayer condensed phase of benzene exhibit the infrared active modes of the gasphase molecule as expected. 相似文献
18.
《Current Applied Physics》2018,18(12):1528-1533
The trajectories of adsorption and dissociation process of O2 on the Al (111) surface were studied by the spin-polarized ab initio molecular dynamics method, and the adsorption activation energy was clarified by the NEB method with hybrid functionals. Three typical dissociation trajectories were found through simulation of O2 molecule at different initial positions. When vertically approaches to the Al surface, the O2 molecule tends to rotate, and the activation energy is 0.66eV. If O2 molecule does not rotate, the activation energy will increase to 1.43 eV, and it makes the O atom enter the Al sublayer eventually. When the O2 molecules parallel approach to the Al surface, there is no activation energy, due to the huge energy released during the adsorption process. 相似文献
19.
The adsorption of CO, O2, and H2O was studied on both the (111) and [6(111) × (100)] crystal faces of iridium. The techniques used were LEED, AES, and thermal desorption. Marked differences were found in surface structures and heats of adsorption on these crystal faces. Oxygen is adsorbed in a single bonding state on the (111) face. On the stepped iridium surface an additional bonding state with a higher heat of adsorption was detected which can be attributed to oxygen adsorbed at steps. On both (111) and stepped iridium crystal faces the adsorption of oxygen at room temperature produced a (2 × 1) surface structure. Two surface structures were found for CO adsorbed on Ir(111); a (√3 × √3)R30° at an exposure of 1.5–2.5 L and a (2√3 × 2√3)R30° at higher coverage. No indication for ordering of adsorbed CO was found on the Ir(S)-[6(111) × (100)] surface. No significant differences in thermal desorption spectra of CO were found on these two faces. H2O is not adsorbed at 300 K on either iridium crystal face. The reaction of CO with O2 was studied on Ir(111) and the results are discussed. The influence of steps on the adsorption behaviour of CO and O2 on iridium and the correlation with the results found previously on the same platinum crystal faces are discussed. 相似文献
20.
《Surface science》1986,175(1):L687-L692
Adsorbed CN may be produced on Pd(111) and Pd(100) surfaces at RT by dissociative adsorption of cyanogen. HREELS measurements show that adsorbed CN forms adsorbed HCN or DCN on these Pd surfaces by reaction with H adsorbed from the residual gas or by dosing with H2 or D2. The reaction temperature is slighly lower for Pd(100) than for Pd(111), and the range of temperatures over which the reaction takes place much narrower. The reaction occurs on a time scale easily monitored with HREELS. 相似文献