洁净和氧吸附的Cu(100)表面重构的理论研究

The interaction of atomic oxygen with the clean Cu(100) surface has been studied by means of cluster and periodic slab models density functional theory in the present paper. The Cu(4,9,4) cluster and a three-layer slab with c(2×2) structure are used to model the perfect Cu(100) surface. Three possible adsorption sites,top, bridge and hollow site, were considered in the calculations. The predicted results show that the hollow site is the prefer site for atomic oxygen adsorbed on Cu(100) surface energetically. This is in good agreement with the experiment. The calculated binding energies are respective 2.014, 3.154 and 3.942 eV for top, bridge and hollow sites at mPW1PW91/LanL2dz level for the cluster model. The geometry of Cu(100) surface has also been optimized theoretically with various density functional methods and the results show that the prediction from the B3PW91/LanL2dz and mPW1PW91/LanL2dz reproduce the experimental observation.The frontier molecular orbitals and partial density of states analysis show that the electron transfer from the d orbital of substrate to the p orbital of the surface oxygen atom.     

丙烯腈在Cu(100)表面化学吸附的密度泛函理论研究

利用密度泛函方法, 模拟金属铜原子簇Cu₁₄(9,4,1)的(100)表面, 对丙烯腈(CH₂＝CHCN)在Cu(100)面上不同吸附位的吸附状况进行了理论研究. 结果表明: 丙烯腈分子通过端位N原子垂直吸附在金属表面上为弱化学吸附, 部分电荷从丙烯腈分子转移至铜金属簇; 由N原子的孤对电子与金属铜形成弱σ共价键; 顶位是最佳吸附位, 吸附能为40.7391 kJ•mol^－1, N原子与金属表面间的平衡距离为0.2279 nm; 其次为桥位和穴位, 吸附能分别为36.2513和30.2158 kJ•mol^－1, 平衡距离为0.2194和0.2886 nm; 吸附后C≡N键的强度降低, 活化了丙烯腈分子. 化学吸附使体系的熵减小, 是由于丙烯腈分子的平动和转动因吸附而被限制.     

Cu(100)表面吸附CN的密度泛函研究

采用密度泛函方法,以原子簇Cu14为模拟表面,对CN自由基分子在垂直和平行Cu(100)表面不同位置的吸附情况进行了研究,结果表明：通过原子C垂直吸附在表面的顶位是其最佳吸附方式,吸附后CN键振动频率发生蓝移;而其它吸附方式中CN键振动频率均发生红移．DOS和电荷转移分析指出CN通过C端吸附在表面顶位位置时,Cu与CN之间具有较强的σ成键和较弱的π反键特征．     

Transient Behavior of the Metal Interface in Lithium Metal–Garnet Batteries

The interface between solid electrolytes and Li metal is a primary issue for solid‐state batteries. Introducing a metal interlayer to conformally coat solid electrolytes can improve the interface wettability of Li metal and reduce the interfacial resistance, but the mechanism of the metal interlayer is unknown. In this work, we used magnesium (Mg) as a model to investigate the effect of a metal coating on the interfacial resistance of a solid electrolyte and Li metal anode. The Li–Mg alloy has low overpotential, leading to a lower interfacial resistance. Our motivation is to understand how the metal interlayer behaves at the interface to promote increased Li‐metal wettability of the solid electrolyte surface and reduce interfacial resistance. Surprisingly, we found that the metal coating dissolved in the molten piece of Li and diffused into the bulk Li metal, leading to a small and stable interfacial resistance between the garnet solid electrolyte and the Li metal. We also found that the interfacial resistance did not change with increase in the thickness of the metal coating (5, 10, and 100 nm), due to the transient behavior of the metal interface layer.     

CoO(100)表面高分辩电子能损失谱与量子化学的从头算

ＣｏＯ（１００）表面高分辩电子能损失谱与量子化学的从头算石守衡（大连轻工业学院基础部物理化学教研室,大连,１１６０３４）关键词ＣｏＯ（１００）表面,高分辩电子能损失谱,从头算Ａ．Ｆｒｅｉｔａｇ等［１］用高辩电子能损失谱研究了ＮｉＯ（１００）表面的电子...     

Density Functional Theory Study on the Adsorption of HCNH and CNH2 on Cu（100） Surface

The HCNH and CNH2 adsorption on different coordination sites of Cu（100） was theoretically studied considering the cluster approach. The present calculations show that the bridge site is the most favorite for CNH2 perpendicularly adsorbed on the Cu（100） surface via the C atom. For HCNH absorbed on the Cu（100） surface, the parallel adsorption mode with the C and N atoms nearly directly above the adjacent top sites of Cu（100） surface is the most favored. Both CNH2 and HCNH are strongly bound to the Cu（100） surface with CNH2 which is lightly stable （2.51 kJ·mol^-1）, indicating that both species may be co-adsorbed on the Cu（100） surface.     

苯分子在Cu(100)面平板模型上吸附的密度泛函理论研究

使用量子化学中的密度泛函理论和平板周期模型方法，研究了苯在Cu(100)面上的吸附方式和相对稳定性. 计算结果表明，苯在Cu(100)表面的吸附属于较强的化学作用，稳定性穴位优于桥位，顶位吸附最不稳定. 在吸附过程中，C—C键有相对大的伸长，C—H键的键长变化较小，但是偏离苯环平面，并背离固体表面，顶位则是朝向表面. 吸附过程中，发生了电子从苯向铜原子的转移.     

氢原子吸附的Cu(100)表面原子结构和电子态

用密度泛函理论的总能计算研究了金属铜(100)面的表面原子结构以及在不同覆盖度时氢原子的吸附状态. 研究结果表明, 在Cu(100)c(2×2)/H表面体系中, 氢原子吸附的位置是在空洞位置, 距最外层Cu原子层的距离为0.052 nm, 相应的Cu—H键长为0.189 nm, 并通过计算结构参数优化否定了其它的吸附位置模型. 总能计算得出Cu(100)c(2×2)/H表面的功函数为4.47 eV, 氢原子在这一体系的吸附能为2.37 eV(以孤立氢原子为能量参考点). 通过与衬底原子的杂化, 氢原子形成了具有二维特征的氢能带结构, 在费米能级以下约0.8 eV处出现的表面局域态是Cu(S)-H-Cu(S-1)型杂化的结果. 采用Cu(100)表面p(1×1)、p(2×2)和p(3×3)的三种氢吸附结构分别模拟1, 1/4, 1/9的原子单层覆盖度, 计算结果表明, 随着覆盖度的增加, 被吸附的氢原子之间的距离变短, 使得它们之间的静电排斥和静电能增大, 从而导致表面吸附能和吸附H原子与最外层Cu原子间垂直距离(ZH-Cu)逐渐减小. 在较低的覆盖度下, 氢原子对Cu(100)表面的影响主要表现为单个原子吸附作用的形式. 通过总能计算还排除了Cu(100)表面(根号2×2根号2)R45°-2H缺列再构吸附模型的可能性.     

甲胺在清洁及磷改性Mo(100)表面的解离

采用广义梯度近似(GGA)的密度泛函理论(DFT)(DFT-GGA)并结合平板模型, 研究了甲胺在清洁及磷(P)改性的Mo(100)表面(P-Mo(100))发生C—N键断裂的反应历程(CH3NH2→CH3+NH2). 优化了裂解过程中反应物、过渡态和产物的几何构型, 获得了反应路径上各物种的吸附能及反应的活化能数据. 计算结果表明, 在清洁和磷改性的Mo(100)表面, 甲胺均稳定吸附在顶位, 甲基和氨基最稳定的吸附位置均为桥位. 甲胺的C—N键在P-Mo(100)表面裂解的活化能为2.39 eV, 高于其在清洁表面的活化能(1.99 eV). 这表明Mo(100)表面被预吸附的P原子钝化了. 电子结构分析表明, 改性P原子使得金属Mo的供电子能力减弱, 导致它的d带中心下移, 从而降低了该表面的反应活性, 提高了甲胺的C—N键裂解的活化能. 活化能的分解表明, C—N键在P-Mo(100)与Mo(100)表面裂解的活化能的差异主要体现在初态到过渡态时甲胺的结构变化引起的能量变化(△EdefCH3NH2)、过渡态仅有甲基存在时的吸附能(ETSCH3)和过渡态甲基和氨基的相互作用(EintCH3…NH2). △EdefCH3NH2和ETSCH3使活化能升高幅度大于EintCH3…NH2使活化能降低幅度, 最终导致甲胺的C—N键在P-Mo(100)表面裂解的活化能要高于在Mo(100)表面裂解的活化能.     

Chemisorption of OCN on Cu (100) surface: a density functional study

The chemisorption of cyanato radial (OCN) on Cu (100) surface is studied by using density functional theory (DFT) and the cluster model method. Cu₁₄ cluster is used to simulate the surface. Vertical bonding geometries with the nitrogen or oxygen atom down, and a parallel bonding geometry are considered, respectively. The present calculations show that cyanato-N species absorbed on the surface is more favorable than the other configurations. It indicates that OCN species is linearly bonded to the Cu (100) surface via the nitrogen atom, and is in good agreement with the experimental result. The cyanato-N species at the bridge site is most stable. For cyanato-N, the calculated symmetric and asymmetric OCN stretch frequencies are all blue-shifted compared with the calculated gaseous values, which is consistent with the experiment result. The charge transfer from the surface to OCN causes a work function increase on the surface. Bonding of OCN to the metal surface is largely ionic.     

H2O在Cu(100)表面吸附的从头算研究

用量子化学从头计算方法,以原子簇Cu₅为模拟表面,研究了水在Cu(100)面上不同吸附位的吸附情况,结果表明:水分子通过氧原子与表面成键,顶位是其最佳吸附位,吸附能约为70kJ/mol,平衡距离为0.213nm,氢原子远离表面.在氧原子不加极化函数时,水分子的二次轴垂直于表面时能量最低,但倾斜至50°所需能量仅在10kJ/mol以内.当考虑O原子d轨道的影响时,水分子倾斜时能量较低,得到了与实验相符的吸附构型.另外还研究了表面电荷对吸附体系的影响,结果表明:表面带正电荷时,水与表面间的相互作用增强,水上所转移电荷增多,Cu-O间平衡距离减小;表面带负电荷时,情况与之相反,且氢原子靠近表面时,势能曲线有最低点.     

Atomic structures and dynamics of a Cu(100) electrode in dilute hydrobromic acid: An in situ STM study

The surface electrochemistry of Cu(100) in 10 mM hydrobromic acid electrolyte has been studied by means of cyclic voltammetry and in situ STM. In the potential range between the onset of the anodic copper dissolution at positive and the hydrogen evolution at negative electrode potentials, the CV of Cu(100) in 10 mM HBr is characterized only by the double-layer charge. Within this potential regime a highly ordered (√2×√2)R45°-superstructure is seen in the STM experiments assigned to specifically adsorbed bromide anions. No desorption of the bromide adlayer has been found in these STM experiments even at extremely negative potentials at the onset of hydrogen evolution. Therefore the bromide desorption potential is concluded to lie within the potential regime of massive hydrogen evolution at even more negative potentials. Adsorbed bromide induces a drastic restructuring and faceting of the surface topography depending on the applied potential. The driving force of this process is the formation of thermodynamically favored copper steps aligned parallel to close packed 100 directions of the bromide adsorbate. Dynamic processes like copper dissolution and deposition are also strongly influenced by the geometry of the (√2×√2)R45° bromide adlayer. Corrosion as well as deposition of copper material follows the close packed 100 directions of the bromide adsorbate. For moderate reaction rates an additional anisotropy between the [001]- and [010]-direction is observed due to the nonequivalence of two different kinds of bromide stabilized copper steps. The origin of these two kinds of steps is the phase relation of close packed adsorbate rows of adjacent terraces. The deposition of copper material does not only start at the lower but unusually, also at the upper sites of step edges leading to the formation of microfacets. Not only the growth of monoatomically high islands is observed but also a double-layer and multilayer growth of copper.     

PdAu(100)和PdAu(111)双金属表面的密度泛函理论研究

采用密度泛函理论(Density Functional Theory DFT)研究Au(100)和Au(111)表面含有不同Pd构型时表面的形成能.结果表明,非连续Pd构型的形成能较连续Pd构型的低,在表面易形成,其中第二临位Pd对构型被证实是乙烯与醋酸结合生成醋酸乙烯反应中催化活性最高的构型.随后计算CO在不同表面Pd原子的顶位吸附能和Pd原子的d带中心,结果显示表面Pd原子与相邻金原子之间几乎没有电子传递,并且PdAu(111)表面的Pd原子d带中心随周围Au原子个数的增加而远离费米能级,伴随着CO在其上吸附能的减小,但是同样的趋势在PdAu(100)表面不存在.最后,通过计算,CO在金属表面的吸附机理为CO成键轨道5σ的电子传递给Pd原子的d带,而Pd原子的d带电子又反馈回CO的反键轨道2π*.     

DOPA醌在Cu(100)表面吸附的密度泛函理论研究

采用广义梯度密度泛函理论(GGA)的BLYP方法结合周期性平板模型,以原子簇Cu41为模拟表面,对DOPA醌分子在Cu(100)表面不同位置的吸附模型进行了构型优化、能量计算以及Mulliken布居分析,结果表明通过相邻的羰基垂直吸附在表面的桥位是其最佳吸附方式,吸附能为247.2310kJ/mol;其次为顶位、顶位R45和穴位,吸附能分别为227.7162kJ/mol、220.7305kJ/mol和217.8456kJ/mol。Mulliken布居分析结果表明整个吸附体系发生了由Cu原子向DOPA醌分子的电荷转移。     

Chemical Reconstruction of Pt-Rh(100) Alloy and Pt/Rh(100), Rh/Pt(100) Bimetallic Surfaces

When Cu(110), Ni(l 10), Ag(110) surfaces are exposed to O₂ at room temperature, one dimensional metal-oxygen strings grow in the < 001 > direction of the (110) surfaces. A similar phenomenon occurs in the adsorption of H₂ on Ni( 110) surface at room temperature, where the one dimensional strings grow along the < 110 > direction. These phenomena are undoubtedly different from the adsorption induced reconstruction but are explained by the chemical reconstruction involving the formation of quasi-compounds and their self-ordering on the metal surfaces. The chemical reconstruction is indispensablly important to understand the structure and catalysis of alloy and bimetallic surfaces. Pt_0.25Rh_0.75(100) alloy surface being active for the reaction of NO with H₂ is an interesting example. When the Pt-Rh(100) alloy surface is exposed to NO or O₂ at arround 500 K, a p(3 × 1) ordered Rh-O over-layer is obtained on a Pt-enriched 2nd layer by the chemical reconstruction. Ordering of Rh-0 in the p(3 × 1) structure on the Pt(100) surface was reproduced by heating a Rh/Pt(100) bimetallic surface in O₂, and the chemical reconstruction making the p(3 × 1) Rh-O overlayer on a Pt enriched 2nd layer was also proved by heating a Pt/Rh(100) bimetallic surface in O₂ or NO. The activation mechanism of the Pt-Rh alloy and the Pt/Rh bimetallic surfaces by the chemical reconstruction was evidently shown by using a Pt deposited Rh(100), Pt/Rh(100), surface. That is, the Pt/Rh(100) is not so active for the reaction of NO with H₂, but the reconstructed p(3 × 1)Rh-O/Pt-layer/Rh(100) surface is very active for the reaction. Therefore, it was concluded that the chemical reconstruction of the Pt-Rh catalyst makes the active surface which is composed of Rh-O and a Pt layer.     

Cu(100)表面吸附HCN和HNC的密度泛函研究

采用密度泛函方法，以原子簇Cul4为模拟表面，对氢氰酸(HCN)和异氰酸(HNC) 在Cu(100)表面上不同吸附位的吸附情况进行了研究．结果表明：HCN和HNC分别通 过原子N和C垂直吸附在表面上时，顶位是其最佳吸附位，且是吸附能为18．5kJ· mol^-1和42．6kJ·mol^-1的弱吸附，计算结果与实验相符．C—N(HCN)键或N—C (NHC)键偏离垂直的分子轴线的吸附体系均不稳定．顶位吸附时HCN和HNC分子的C- N键振动频率均发生蓝移．     

NO在Rh(100),Rh(111)面上吸附与直接分解的密度泛函理论研究

本文应用第一性原理的密度泛函(DFT)方法,使用DMol³计算程序,对NO在Rh(100)和Rh(111)面上的吸附与分解进行量化计算,力图解决NO在Rh(100)和Rh(111)面上的优选吸附位、直接分解的过渡态和活化能等重要问题.