Adsorption and Vibration of CI Atoms on Ni Low-index Surfaces

The 5-parameter Morse potential（5-MP） of the interactions between Cl atoms and Ni surfaces was constructed. The adsorption and diffusion of Cl atoms on Ni low index-surfaces were investigated with 5-MP in detail. All the critical characteristics of the system, such as adsorption site, adsorption geometry, binding energy, eigenvalues for vibration, etc. were obtained. The calculated results show that chlorine atoms are likely to be adsorbed on the high symmetry- sites. Cl atoms locate on the four-fold hollow sites of the intact Ni（100） surface, while they tend to occupy threefold sites on the Ni（ 111 ） surface. The four-fold hollow sites are the most stable adsorption sites on the Ni （110） surface for Cl, although the three-fold sites and the long-bridge sites are stable adsorption sites on the Ni（110） surface for the atoms of the first and second periods. For the Cl-Ni surface adsorption system, the surface binding energy of a Cl atom is relevant to the coarse degree of the cluster surface, and the binding energies have an order of Ni （ 111 ） 〈 Ni（100） 〈Ni（100）.     

A DFT Study of CO Adsorption on the Cu2O（111） Surface with Oxygen Vacancy

First-principles calculations based on density functional theory （DFr） and the generalized gradient approximation （GGA） have been used to study the adsorption of CO molecule on the Cu2O（111） oxygen-vacancy surface. Calculations indicate that the C-O bond is weakened upon adsorption compared with that over perfect surface. In addition, with the density increase of the defective sites, the adsorption energies of the defect-CO configuration increase whereas the C-O bond nearly remains constant.     

Theoretical Study on the Adsorption and Decomposition of Methanol over the Pt-Mo（111）/C Surface

The density functional theory(DFT) and self-consistent periodic calculation were used to investigate the methanol adsorption on the Pt-Mo(111)/C surface.The adsorption energies,equilibrium geometries and vibration frequencies of CH3OH on nine types of sites on the Pt-Mo(111)/C surface were predicted and the favorite adsorption site for methanol is the top-Pt site.Both sites of valence and conduction bands of doped system have been broadened,which are favorable for electrons to transfer to the cavity.The possible decomposition pathway was investigated with transition state searching and the calculation results indicate that the O-H bond is first broken,and then the methanol decomposes into methoxy.The activation barrier of O-H bond breaking with Pt-Mo catalyst is only 104.8 kJ mol-1,showing that carbon supported Pt-Mo alloys have promoted the decomposition of methanol.Comparing with the adsorption energies of CH3OH on the Pt(111)/C surface and that of CO,the adsorption energies of CO are higher,and Pt(111)/C is liable to be oxidized and loses the activity,which suggests that the catalyst Pt-Mo(111)/C is in favor of decomposing methanol and has better anti-poisoning ability than Pt(111)/C.     

Density Functional Theory Study of C2Hx（x=4～6） Adsorption on the Fe（110） Surface

The density functional theory(DFT) and self-consistent periodic calculation were used to investigate the C2Hx(x = 4～6) species adsorption on the Fe(110) surface. The adsorption energy and equilibrium geometry of the species C2Hx(x = 4～6) on four possible sites(top,hcp,SB and LB) on the Fe(110) surface were predicted and compared. Mulliken charges and density of states analysis of the most stable site have been discussed. It is found that the species of C2H6 and C2H5 are adsorbed strongly on the Fe(110) surface with calculated adsorption energy of -80.24 and -178.89 kJ·mol-1 at the Fe-LB(long-bridge) ,respectively. However,the C2H4 is adsorbed strongly on the Fe(110) surface with calculated adsorption energies of -114.96 kJ·mol-1 at the top. The results indicate that the charge transferring process can be completed by chemisorption between Fe(110) surface and the species. Moreover,the chemical bands can be formed by chemisorptions between the Fe(110) surface and the species,too.     

Density Functional Theory Studies on the Adsorption of CO2 on Different CaO Surfaces

Carbon dioxide adsorbed on different kinds of CaO surfaces has been investigated with the help of the first principle density functional theory plane wave calculations. Various possible configurations have been considered and the calculated results showed that CO2 was strongly adsorbed by C atom bonded with the CaO （001） and （110） surfaces with adsorption energies of 1.38 and 3.22 eV, respectively. The adsorption of CO2 molecule on defect surfaces is complicated compared with that on the pristine surfaces. The adsorption energy of CO2 absorbed on the CaO（110） surface is larger than that of CaO（001） surface when the type of defect surface is the same.     

Theoretical Study of NO Dimer Adsorption and Dissociation on the CuCr2O4 （100） Surface

Theoretical simulation of the adsorption and dissociation of two NO molecules at the Cu^2＋, Cr^3＋ and bridge Cr^3＋ sites （b-Cr^3＋） on the normal spinel CuCr2O4 （100） surface has been carried out by density functional theory calculations. The results show that the formed N-down and O-down NO dimers are negatively charged. The formation of stable O-down dimers on the surface leads to the great elongation of N-O bond, which contributes to the NO reduction. The transition-state calculations indicate that the decomposition of O-down NO dimer at the b-Cr^3＋ site is most favorable and N2O is the major reduction product.     

Density Functional Theory Study on the Adsorption of CN on Transition Metal M（100） （M = Ni,Pd, Pt,Cu, Ag and Au） Surfaces

The adsorption of cyanide on the top site of a series of transition metal M（100） （M = Cu, Ag, Au, Ni, Pd, Pt） surfaces via carbon and nitrogen atoms respectively, with the CN axis perpendicular to the surface, has been studied by means of density functional theory and cluster model. Geometry, adsorption energy and vibrational frequencies have been determined, and the present calculations show that the adsorption of CN through C-end on metal surface is more favorable than that via N-end for the same surface. The vibrational frequencies of CN for C-down configuration on surface are blue-shifted with respect to the free CN, which is contrary to the change of vibrational frequencies when CN is adsorbed by N-down structure. Furthermore, the charge transfer from surface to CN causes the increase of surface work function.     

First-principles Study on the Properties of CaO(100) Surface Adsorbing Carbon Dioxide

The increasing carbon dioxide emissions have a huge impact on the global environment. Carbonation reaction of CaO is regarded as a potential method to capture carbon dioxide. The density functional theory calculations have been performed to investigate the adsorption of CO_2 on CaO(100) surface. This paper systematically studied the adsorption of CO_2 at different adsorption sites on CaO(100) surface and the influence of adsorption angle on adsorption energy. Based on the studying of adsorption sites, adsorption energy and electronic structure of the CO_2/CaO(100) systems, chemical adsorption mainly happens when CO_2 molecules are absorbed on the CaO(100) surfaces, but physical adsorption may also happen. The research found that CO_2 molecules reacted with surface O atom through C, forming monodentate surface carbonate species and tridentate carbonate. Among them, low-coordinated monodentate ligands have a higher stability than tridentate ligands due to the shorter C–OS bond length of monodentate ligands.     

Density Functional Study of the C Atom Adsorption on the α-Fe2O3 （001） Surface

The adsorption of C atoms on the α-Fe2O3(001) surface was studied based on density function theory(DFT) ,in which the exchange-correlation potential was chosen as the PBE(Perdew,Burke and Ernzerhof) generalized gradient approximation(GGA) with a plane wave basis set. Upon the optimization on different adsorption sites with coverage of 1/20 and 1/5 ML,it was found that the adsorption of C atoms on the α-Fe2O3(001) surface was chemical adsorption. The coverage can affect the adsorption behavior greatly. Under low coverage,the most stable adsorption geometry lied on the bridged site with the adsorption energy of about 3.22 eV;however,under high coverage,it located at the top site with the energy change of 8.79 eV. Strong chemical reaction has occurred between the C and O atoms at this site. The density of states and population analysis showed that the s,p orbitals of C and p orbital of O give the most contribution to the adsorption bonding. During the adsorption process,O atom shares the electrons with C,and C can only affect the outermost and subsurface layers of α-Fe2O3;the third layer can not be affected obviously.     

A DFT Study of Thiophene Adsorption on the Rh（111） Surfaces

Thiophene adsorption on the Rh(111) surfaces has been investigated by density functional theory.The results show that the adsorption at the hollow and bridge sites is the most stable.The molecular plane of the thiophene ring is distorted,the C=C bond is stretched to 1.448  and the C-C bond is shortened to 1.390.The C-H bonds tilt 22～42oaway from the surface.The calculated adsorption geometries are in reasonable agreement with population analysis and density of states.The thiophene molecule obtains 0.74 electrons,reflecting the interaction between the lone pair of sulfur and the d-orbitals of metal.The reaction paths and transition states for desulfurization of the molecule have been investigated.The bridge adsorption structure of thiophene leads to a thiol via an activated reaction with an energetic barrier of 0.30 eV.This second step is slightly difficult,and dissociation into a C4H4 fragment and a sulfur atom is possible,with an energetic barrier of 0.40 eV.     

Adsorption of atoms on cu surfaces: a density functional theory study

The chemisorption of atoms (H, N, S, O, and C) on Cu surfaces has been systematically studied by the density functional theory generalized gradient approximation method with the slab model. Our calculated results indicate that the orders of the adsorption energy are H < N < S < O < C on Cu(111) and H < N < O < S < C on Cu(110) and Cu(100). Furthermore, the adsorption energies of the given atoms on Cu(100) are larger than those on Cu(111) and Cu(110). The preferred adsorption sites are a 3-fold hollow site on Cu(111) and a 4-fold hollow site on Cu(100), but the preferred adsorption sites on Cu(110) are different for different adatoms. The energy, as well as the geometry, is in good agreement with the experimental and other theoretical data. In addition, this study focuses on the electronic and geometric properties of the metal-atom (M-A) bond to explain the difference in adsorption energies among adatoms. A detailed investigation of the density of states curves explains the nature of the most stable site. Finally, we test the effect of the coverage and find that the surface coverage has no influence on the preferred adsorption sites of the given adatoms on Cu(110) with the exception of hydrogen and oxygen, but has much influence on the value of the adsorption energy.     

Ab initio study of ternary complexes X:(HCNH)(+):Z with X, Z = NCH, CNH, FH, ClH, and FCl: diminutive cooperative effects on structures, binding energies, and spin-spin coupling constants across hydrogen bonds

Ab initio calculations have been performed on a series of complexes in which (HCNH)(+) is the proton donor and CNH, NCH, FH, ClH, and FCl (molecules X and Z) are the proton acceptors in binary complexes X:HCNH(+) and HCNH(+):Z, and ternary complexes X:HCNH(+):Z. These complexes are stabilized by C-H(+)···A and N-H(+)···A hydrogen bonds, where A is the electron-pair donor atom of molecules X and Z. Binding energies of the ternary complexes are less than the sum of the binding energies of the corresponding binary complexes. In general, as the binding energy of the binary complex increases, the diminutive cooperative effect increases. The structures of these complexes, data from the AIM analyses, and coupling constants (1)J(N-H), (1h)J(H-A), and (2h)J(N-A) for the N-H(+)···A hydrogen bonds, and (1)J(C-H), (1h)J(H-A), and (2h)J(C-A) for the C-H(+)···A hydrogen bonds provide convincing evidence of diminutive cooperative effects in these ternary complexes. In particular, the symmetric N···H(+)···N hydrogen bond in HCNH(+):NCH looses proton-shared character in the ternary complexes X:HCNH(+):NCH, while the proton-shared character of the C···H(+)···C hydrogen bond in HNC:HCNH(+) decreases in the ternary complexes HNC:HCNH(+):Z and eventually becomes a traditional hydrogen bond as the strength of the HCNH(+)···Z interaction increases.     

A Model Calculation for the Isomerization and Decomposition of Chemisorbed HCN on the Si(100)-2×1 Surface

Ab initio molecular orbital and hybrid density functional theory calculations have been performed to study the adsorption, isomerization, and decomposition of HCN on Si(100)-2×1 using the Si₉H₁₂ cluster model of the surface. The results of our calculations indicate that the HCN can adsorb molecularly without a barrier onto the surface with both end-on (LM1) and side-on (LM2) positions. LM1 can isomerize to LM2 with a small barrier of 8 kcal/mol. The isomerization of LM2 by H-migration from C to the N atom, requires 76 kcal/mol activation energy (c.f. 47.5 kcal/mol in the gas phase) because of surface stabilization. Both HCN(a) and HNC(a) end-on adsorbates were found to dissociate readily, as concluded in our earlier experiment, to produce H and CN adspecies. The computed vibrational frequencies of HCN, CN, and also HCNH adspecies agree reasonably well with those observed experimentally. HCNH was found to be stable, with either the C or the N attaching to the surface.     

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。     

Structure and bonding of alkanethiols on Cu(111) and Cu(100)

The local structure of the sulfur atom of methanethiolate and ethanethiolate on the Cu(111) and Cu(100) surfaces was investigated from first principles employing the periodic supercell approach in the framework of density functional theory. On the 111 surface, we investigated the (square root 3 x square root 3)R30 degrees and (2 x 2) structures, whereas on the 100 surface, we investigated the p(2 x 2) and c(2 x 2) structures. The landscape of the potential energy surface on each metal surface presents distinctive features that explain the local adsorption structure of thiolates found experimentally. On the Cu(111) surface, the energy difference between the hollow and bridge sites is only 3 kcal/mol, and consequently, adsorption sites ranging from the hollow to the bridge site were observed for increasing surface coverages. On the Cu(100) surface, there is a large energy difference of 12 kcal/mol between the hollow and bridge sites, and therefore, only the 4-fold coordination was observed. The high stabilization of thiolates on the hollow site of Cu(100) may be the driving force for the pseudosquare reconstruction observed experimentally on Cu(111). Density of states analysis and density difference plots were employed to characterize the bonding on different surface sites. Upon interaction with the metal d bands, the pi* orbital of methanethiolate splits into several peaks. The two most prominent peaks are located on either edge of the metal d band. They correspond to bonding and antibonding S-Cu interactions. In the case of ethanethiolate, all the back-bonds are affected by the surface bonding, leading to alternating regions of depletion and accumulation of charge in the successive bonds.     

Adsorption and reactions of ClCH2CH2OH on clean and oxygen-precovered Cu(100): experimental and computational studies

Temperature-programmed reaction/desorption, reflection-absorption infrared spectroscopy, and density functional theory calculations have been employed to investigate the adsorption and thermal reactions of ClCH2CH2OH on clean and oxygen-precovered Cu(100) surfaces. On Cu(100), ClCH2CH2OH is mainly adsorbed reversibly. The ClCH2CH2OH molecules at a submonolayer coverage can change their orientation with increasing temperature. However, on oxygen-precovered Cu(100), all of the adsorbed ClCH2CH2OH molecules below 0.5 langmuir exposures completely dissociate to generate ethylene and acetaldehyde via the intermediate of ClCH2CH2O-. The computational studies predict that the ClCH2CH2O- is most likely to be adsorbed at the 4-fold hollow sites of Cu(100), with its C-O bond only slightly titled away from the surface normal and with a gauche conformation with respect to the C-C bond. The hollow-site ClCH2CH2O- has an adsorption energy that is 4.4 and 19.2 kcal x mol(-1) lower than that of the ClCH2CH2O- bonded at the bridging and atop sites, respectively. No significant effect of precovered oxygen on the ClCH2CH2O- bonding geometry and infrared band frequencies has been observed, as compared with the case without oxygen.     

CO2 和C2 H4 光催化合成丙烯酸的Cu/ZnO-TiO2 催化剂

The metallic Cu modified n-p coupled semiconductor Cu/ZnO-TiO2 was prepared by the sol gel method, and its surface structure, absorptivity of ultraviolet light, chemisorption properties and photocatalytic behaviors were investigated by techniques of X-ray diffraction (XRD), Transmission Electron Microscopy (TEM), BET surface area (BET), Infrared absorption spectra (IR), UV-visible diffused reflectance spectra (UV-vis) and photo stimulated surface catalytic reaction. The results show that the main crystal structure of the catalyst is anatase TiO2 with the particle size about 10 nm. The Zn-O-Ti bond is formed and the absorption intensity in the wavelength region of 250～400 nm is enhanced through the coupling of ZnO and TiO2, while the absorption region is expanded to visible light with the UV absorbance limit shifting to the shorter wavelength region after Cu supported on the coupled semiconductor ZnO-TiO2. The adsorption states of reactants are important factors influencing the results of photocatalytic reaction, while the bridge adsorption state of CO2 formed on Cu and Lewis acid sites Ti4+ and undissociated of C2H4 formed on Cu and Lewis base sites bridge-O are the effective intermediates to synthesize the crylic acid with the selectivity over 87% under the temperature of 100℃.     

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.     

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.     

甲醇在FeS2(100)完整表面的吸附和分解

采用基于第一性原理的密度泛函理论结合周期平板模型方法, 研究了甲醇分子在FeS₂(100)完整表面的吸附与解离. 通过比较不同吸附位置的吸附能和构型参数发现: 表面Fe位为有利吸附位, 甲醇分子通过氧原子吸附在表面Fe位, 吸附后甲醇分子中的C―O键和O―H键都有伸长, 振动频率发生红移; 甲醇分子易于解离成甲氧基CH3O和H, 表面Fe位仍然是二者有利吸附位. 通过计算得出甲醇在FeS₂(100)表面解离吸附的可能机理: 甲醇分子首先发生O―H键的断裂, 生成甲氧基中间体, 继而甲氧基C―H键断裂, 得到最后产物HCHO和H₂.