Theory Study of the Adsorption of Hydrocyanic Acid onto Small Silver Clusters

Density functional theory calculations have been performed to study the interaction of small silver clusters, Ag2 ~Ag9, with HCN. The adsorption of HCN on-top site of the silver cluster, among various possible sites, is energetically preferred. The adsorption energies of HCN on the silver clusters reach a local maximum at n = 4, which is only about 0.450 eV, indicating that the adsorbed HCN molecule is weakly perturbed. The adsorbed C–N and C–H stretching frequencies are blue- and red-shifted compared with the values of free HCN, respectively.     

Density Functional Theory Study on the Adsorption of Dioxygen on Small Pt-Pd Clusters

1 INTRODUCTION The bimetallic nanoclusters are of standing inte- rest since they can exhibit catalytic, electronic and optical properties distinct from those of corre- sponding pure nanoclusters[1～4]. Palladium and pla- tinum, well known for their catalytic properties, are often used as the catalyst in different fuel cells[5～8]. Several experimental results illustrate that for the oxygen reduction reaction (ORR), which is one of the primary reactions taking place in many fuel cells and…     

Adsorption Study of Methane on Activated Meso-carbon Microbeads by Density Functional Theory

A combined method of density functional theory (DFT) and statistics integral equation (SIE) for the determination of the pore size distribution (PSD) is developed based on the experimental adsorption data of nitrogen on activated mesocarbon microbead (AMCMB) at 77K. The pores of AMCMB are described as slit-shaped with PSD.Based on the PSD, methane adsorption and phase behavior are studied by the DFT method. Both nitrogen and methane molecules are modeled as Lennard-Jones spherical molecules, and the well-known Steele‘s 10-4-3 potential is used to represent the interaction between the fluid molecule and the solid wall. In order to test the combined method and the PSD model, the Intelligent Gravimetric Analyzer (IGA-003) was used to measure the adsorption of methane on the AMCMB. The DFT results are in good agreement with the experimental data. Based on these facts,we predict the adsorption amount of methane, which can reach 32.3ω at 299K and 4 MPa. The results indicate that the AMCMBs are a good candidate for adsorptive storage of methane and natural gas. In addition, the capillary condensation and hysteresis phenomenon of methane are also observed at 74.05K.     

苯在CuCl（111）表面吸附的密度泛函理论研究

采用量子化学的密度泛函理论方法,探讨了苯分子在CuCl(111)表面上不同覆盖度下不同吸附位上的平行吸附行为. 计算结果表明,随覆盖度的减小,吸附作用增强, Cl位上的吸附是稳定的吸附模式,在低覆盖度下吸附能约为74 kJ/mol, 在顶位和穴位上的吸附属于较弱的物理吸附. 同时对吸附前后的电子布居和态密度进行了分析. 吸附过程中,苯分子的π电子向底物转移,同时Cu的 3d轨道的电子反馈给苯的反键π轨道.     

二甲醚在Pt(100)表面吸附的密度泛函理论研究

采用密度泛函理论(DFT)方法结合周期性平板模型,研究了二甲醚(DME)分子在Pt(100)表面上的吸附.通过对不同吸附位(顶位、空位和桥位)下的几何结构、吸附能和mulliken电荷布局计算发现,吸附后C-O键和C-H键都有不同程度的伸长,top位的吸附能最大,hcp位最小;top位吸附有利于C-O键的断裂,bri位吸附则更利于C-H键的断裂。     

A Periodic Density Functional Study on Adsorption Properties of Methoxy on Au（111） Surface

1INTRODUCTION Methoxy(CH3O)has been identified as the first intermediate in the decomposition of methanol on extensive list of clean transition metal surfaces,such as Ni(100)[1],Cu(100)[2,3],Cu(111)[4],Ag(111)[5],Au(110)[6],Pd(111)[7]and Ru(0001)[8].The electronic structure of the metal is a determining factor in OH bond scission.In fact,group IB clean surfaces have shown very low activity towards this reaction,al-though there are reports on low amounts of methoxy formed on clean Cu(…     

A Density Functional Theory Study on the Adsorption of CN on Ni(111) Surface

1 INTRODUCTION Cyanide, CN, is an important free-radical mole-cule of one carbon chemistry, organic chemistry, free-radical chemistry and cosmochemistry. And the im-portant industrial processes, such as the Andrussovreaction, depend on the reactivity of CN bond[1]. Thechemistry of cyanide is also important in the surfacechemistry of a number of C- and N-containing sys-tems[1, . During the past decade, the adsorption of 2]CN and CN-containing molecules on transition metalsurfa…     

HCN Adsorption on the Fe(100), Fe(111) and Fe(110) Surfaces: a Density Functional Theory Study

Twenty kinds of adsorptions of HCN on the Fe(100), Fe(111) and Fe(110) surfaces at the 1/4 monolayer coverage are found using the density functional theory. For Fe(100), the adsorption energy of the most stable configuration where the HCN locates at the fourfold site with the C-N bonded to four Fe atoms is 1.928 eV. The most favored adsorption structure for HCN on Fe(111) is f-η3(N)-h-η3(C), in which the C-N bond is almost parallel to the surface, and the adsorption energy is 1.347 eV. On Fe(110), the adsorption energy in the most stable configuration in which HCN locates at the two long-bridge sites is 1.777 eV. The adsorption energy of the parallel orientation for HCN is larger than that of the perpendicular configuration. The binding mechanism of HCN on the Fe(100), Fe(111) and Fe(110) surfaces is also analyzed by Mulliken charge population and the density of states in HCN. The result indicates that the configurations in which the adsorbed HCN becomes the non-linear are beneficial to the formation of the addition reaction for hydrogen. The nature that the introduction of Fe into the catalyst could increase the catalytic activity of the bimetallic catalyst in the addition reaction of hydrogen for nitriles is revealed.     

Modeling of Adsorption in Finite Cylindrical Pores by Means of Density Functional Theory

Adsorption of argon at its boiling point in finite cylindrical pores is considered by means of the non-local density functional theory (NLDFT) with a reference to MCM-41 silica. The NLDFT was adjusted to amorphous solids, which allowed us to quantitatively describe argon adsorption isotherm on nonporous reference silica in the entire bulk pressure range. In contrast to the conventional NLDFT technique, application of the model to cylindrical pores does not show any layering before the phase transition in conformity with experimental data. The finite pore is modeled as a cylindrical cavity bounded from its mouth by an infinite flat surface perpendicular to the pore axis. The adsorption of argon in pores of 4 and 5 nm diameters is analyzed in canonical and grand canonical ensembles using a two-dimensional version of NLDFT, which accounts for the radial and longitudinal fluid density distributions. The simulation results did not show any unusual features associated with accounting for the outer surface and support the conclusions obtained from the classical analysis of capillary condensation and evaporation. That is, the spontaneous condensation occurs at the vapor-like spinodal point, which is the upper limit of mechanical stability of the liquid-like film wetting the pore wall, while the evaporation occurs via a mechanism of receding of the semispherical meniscus from the pore mouth and the complete evaporation of the core occurs at the equilibrium transition pressure. Visualization of the pore filling and empting in the form of contour lines is presented.     

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．     

Density Functional Theory Study of the Adsorption of C2H2 on the Cu/Pt(111) Bimetallic Surfaces

We applied periodic density-functional theory to investigate the adsorption of C2H2 on the Cu/Pt bimetallic and monometallic surfaces, including Cu-Pt-Pt and Pt-Cu-Pt representing the monolayer Cu on the Pt surface and subsurface Cu in the Pt surface, respectively. For the Pt(111) and Pt-Cu-Pt surfaces, C2H2 is preferentially a 3-fold "parallel-bridge" configuration, and a "μ-bridge" structure exists above the Cu(111) and Cu-Pt-Pt surfaces. The adsorption energy of C2H2 on these surfaces decreases in the order Pt(111) > Cu-Pt-Pt > Pt-Cu-Pt > Cu(111). The analysis of density of states, charge, and vibrational frequencies showed obviously weakening of the adsorbed C-C bond and high sp2 character on the carbon atom. Furthermore, when the top-layer compositions are equal, the nearer the EF d-band center is, the larger the C2H2 adsorption energy will be.     

The Structural and Electronic Properties of Tin-Based Heteroatom Clusters Studied by the Density Functional Theory

The focus of this study is on compound clusters and, due to the existence of many phases with different structural properties, tin-based materials have been chosen as the reference case. The clusters considered below are of two types: in the first case the clusters have the skeleton of the pure tin clusters and are doped with oxygen and aluminum atoms with composition Sn _x Y _y with Y = Al, O, x = 1, 10 and y = 1, 2. In the second case the clusters have a rutile lattice with a columnar or a spherical shape and a size up to 80 atoms and are doped with a number of aluminum atoms up to 20. The calculations are based on the Density Functional Theory (DFT) and the results describe the cluster structure, its binding energy and the density of states (DOS). The general indication of the calculations is that the additive coordinates outside, rather than inside, the pristine skeleton with the formation of hybrid bonds with properties similar to the ones of the host atoms. Also conspicuous effects of hybridization are observed in the electronic structure and, due to these effects, the binding energy may decrease with respect to the one in the undoped clusters.     

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.     

簇模型ZnO(100)面上吸附CO_2的密度泛函理论研究

采用电荷自洽方法, 以嵌入原子簇Zn4O4为模型, 使用量子化学的密度泛函理论, 研究了二氧化碳在六方ZnO非极化的(1010)面的可能吸附态。计算表明, CO2垂直底物表面吸附, 氧原子只能与Zn原子配位, 并且吸附能为很弱的1.8 kJ/mol;吸附质分子平行于底物表面时, 得到了5种平衡吸附构型, 其中采用CZn配位和η2O, O二齿配位时, 吸附很弱, 经BSSE校正后的吸附能在8.8~6.6 kJ/mol。 采用η2C, O方式分别与O和Zn配位时, 吸附能为31.1 kJ/mol; C原子与表面O配位时计算得到了唯一的一个化学吸附态, 吸附能为139.6 kJ/mol, 与实验结果一致。     

铜族金属与完整及氮掺杂石墨烯的相互作用

基于广义梯度密度泛函理论和周期平板模型,研究了铜族金属单原子和双原子簇与完整及氮掺杂石墨烯的结合情况.结果表明,氮掺杂后石墨烯的电子结构特性由半金属性变为金属性;铜族金属在完整及石墨型氮掺杂石墨烯上的吸附较弱,结合能约为0.5eV,而在吡啶型氮掺杂和吡咯型氮掺杂石墨烯上有较强的化学吸附,结合能一般大于1eV;吡咯型氮掺杂后的构型不稳定,金属原子及簇与包含该结构的石墨烯衬底作用时会使其向吡啶型氮掺杂转变,并最终得到基于吡啶型氮掺杂的稳定吸附构型.Mulliken电荷布居分析显示,吸附在吡啶型氮掺杂石墨烯上的金属单原子与金属双原子簇带电性质相反.态密度及轨道分析表明,Cu与吡啶型氮掺杂石墨烯空位处留有悬挂键的三个原子成键,而Au与其中两个C原子成键.     

氧在CuCl(111)表面吸附的密度泛函理论研究

运用广义梯度密度泛函理论的PW91方法结合周期平板模型,在DNP基组下研究了氧分子和氧原子在CuCl(111)表面上的吸附.对氧分子在CuCl(111)表面吸附的相关计算和比较发现,覆盖度为0.25单层时的吸附构型为稳定的吸附构型,氧分子倾斜地吸附在CuCl(111)表面的顶位时比较稳定,吸附后O2分子的伸缩振动频率与自由O2分子相比发生了红移.态密度和Mulliken电荷布居分析结果表明,整个吸附体系发生了由Cu原子向O2分子的电荷转移.氧原子在CuCl(111)表面吸附的计算结果表明,氧原子倾向于以穴位(hollow)吸附在CuCl(111)表面,通过Mulliken电荷布居和态密度分析对氧原子在CuCl表面的吸附行为作了进一步探讨.     

Rh(111)表面上CO和O共吸附的密度泛函理论计算研究

采用密度泛函理论对Rh(111)表面上CO和O的吸附和共吸附进行了系统的研究,计算了三类不同的共吸附结构.从吸附能和化学位移的角度,通过与已有实验结果对比,推断出可能存在的吸附构型.CO和O之间存在较大的排斥作用,在表面上竞争吸附.电子结构分析发现,这种排斥作用来源于CO和O之间与Rh的d轨道成键的竞争.用密度泛函理论计算的化学位移与实验测量结果一致,说明化学位移的理论计算能辅助对表面结构的预测.     

Adsorption of Co2B2 and Ni2B2 Clusters on the TiO2 (110) Surface: a Density Functional Study

Based on density functional theory and generalized gradient approximation calculations, the adsorption of Co2B2 and Ni2B2 clusters on the rutile TiO2 (110) surface has been investigated utilizing periodic supercell models. Unambiguously, the results demonstrate that the hollow site turns out to be preferable for Co2B2 cluster while Ti2 site is for Ni2B2 cluster to adsorb. Orbital population analysis indicates a strong interaction between Co2B2 and O atom of TiO2 surface, which can be attributed to the overlap of Co 3d and surface O 2p orbital. Similarly, for Ni2B2 , the bonding interaction occurs mostly through the interaction of Ni 3d/4s and O 2p orbitals. Note that, there is also an interaction within the Co2B2 clusters (Ni2B2) through B 2s/2p and Co 3d orbitals (Ni 3d/4s). Moreover, orbital analysis results shows that the strong bonding between Ni2B2 and Ti2 site is due to the overlap of HOMO of Ni2B2 and d-orbital of five-coordinated titanium atoms.     

A Density Functional Study on the Geometries of Compounds Fe(HCN)_n~+ (n = 1～6)

1 INTRODUCTION The solvation of metal ion by different types ofsolvents is of great interest for a wide variety of app-lications[1]. In the experimental and theoretical inve-stigations, most of such studies are focused on ion-ligand systems complexed by…