Adsorption and Reaction of CO on （100） Surface of SrTiO3 by Density Function Theory Calculation

Adsorption and reaction of CO on two possible terminations of SrTiO3 （100） surface are investigated by the first-principles calculation of plane wave ultrasoft pseudopotentiai based on the density function theory. The adsorption energy, Mulliken population analysis, density of states （DOS） and electronic density difference of CO on SrTiO3 （100） surface, which have never been investigated before as far as we know are performed. The calculated results reveal that the Ti-CO orientation is the most stable configuration and the adsorption energy （0.449eV） is quite small. CO molecules adsorb weakly on the SrTiO3 （100） surface, there is predominantly electrostatic attraction between CO and the surface rather than a chemical bonding mechanism.     

A density functional theory study on the adsorption of CO and O2 on Cu-terminated Cu2O （111） surface

The adsorptions of CO and 02 molecules individually on the stoichiometric Cu-terminatcd Cu20 （111） surface are investigated by first-principles calculations on the basis of the density functional theory. The calculated results indicate that the CO molecule preferably coordinates to the Cu2 site through its C atom with an adsorption energy of-1.69 eV, whereas the 02 molecule is most stably adsorbed in a tilt type with one O atom coordinating to the Cu2 site and the other O atom coordinating to the Cul site, and has an adsorption energy of -1.97 eV. From the analysis of density of states, it is observed that Cu 3d transfers electrons to 2π orbital of the CO molecule and the highest occupied 5σ orbital of the CO molecule transfers electrons to the substrate. The sharp band of Cu 4s is delocalized when compared to that before the CO molecule adsorption, and overlaps substantially with bands of the adsorbed CO molecule. There is a broadening of the 2π orbital of the 02 molecule because of its overlapping with the Cu 3d orbital, indicating that strong 3d-2π interactions are involved in the chemisorption of the 02 molecule on the surface.     

Band Structures of Metal-Oxide Capped Graphene： A First Principles Study

We perform a first-principles calculation based on density functional theory to investigate the interface between single layer graphene and metal oxides. Our study reveals that the monolayer graphene becomes semiconducting by single crystal SiO2 and Al2O3 contact, with energy gaps to - 0.9 and - 1.8 eV, respectively. We find the gap originates from the breakage of π bond integrity, whose extent is related to the interface atom configuration. We believe that our results highlight a promising direction for the feasibility to apply large scale graphene layers as building blocks in future electronics devices.     

Comparative study of adsorption characteristics of Cs on the GaN （0001） and GaN （0001） surfaces

The adsorption characteristics of Cs on GaN （0001） and GaN （0001） surfaces with a coverage from 1/4 to 1 monolayer have been investigated using the density functional theory with a plane-wave uttrasoft pseudopotential method based on first-principles calculations. The results show that the most stable position of the Cs adatom on the GaN （0001） surface is at the N-bridge site for 1/4 monolayer coverage. As the coverage of Cs atoms at the N-bridge site is increased, the adsorption energy reduces. As the Cs atoms achieve saturation, the adsorption is no longer stable when the coverage is 3/4 monolayer. The work function achieves its minimum value when the Cs adatom coverage is 2/4 monolayer, and then rises with Cs atomic coverage. The most stable position of Cs adatoms on the GaN （000i） surface is at H3 site for 1/4 monolayer coverage. As the Cs atomic coverage at H3 site is increased, the adsorption energy reduces, and the adsorption is still stable when the Cs adatom coverage is 1 monolayer. The work function reduces persistently, and does not rise with the increase of Cs coverage.     

A Density Functional Study of Atomic Carbon Adsorption on δ-Pu（111） Surface

Adsorption of atomic carbon on 6-Pu（111） surface is investigated systematically using density functional theory with RPBE functional. The adsorption energies, adsorption structures, Mulliken population, work functions, layer and projected density of states are calculated in wide ranges of coverage, which have never been studied before as far as we know. It is found that the hcp-hollow sites is the energetically favorable site for all the coverage range considered. The repulsive interaction is identified, and the adsorption energy decreases with the coverage, while work function increases linearly with the coverage. It is found that the C-Pu interaction is very strong due to the hybridization between the C 2p states and the Pu 5 f , Pu 6p,Pu 6d states of topmost layer Plutonium atoms.     

First-Principle Study of H2 Adsorption on Mg3N2（ll0） Surface

The adsorption of H2 on two kinds of Mg3N2（110） crystal surface is studied by first principles. Adsorption sites, adsorption energy, and the electronic structure of the Mg3N2（110）/H2 systems are calculated separately. It is found that H2 is mainly adsorbed as chemical adsorption, on these sites the 1-12 molecules are dissociated and the H atoms tend to the top of two N, respectively, forming two NH, or the H atoms tend to the same N forming one NH2. There are also some physicM adsorption sites. One of the bridge sites of Mg3N2 （110） surface is more favorable than the other sites. On this site, H atoms tend to the top of two N, forming two NH. This process belongs to strong chemical adsorption. The interaction between 1-12 molecule and Mg3N2（110） surface is mainly due to the overlap-hybridization among Hls, N 2s, and N 2p states, covalent bonds are formed between the N and H atoms.     

First Principles Study of Half Metallic Properties of VSb Surface and VSb/GaSb （001） Interface

The structural, electronic, and magnetic properties of VSb in zincblende, and NiAs phases, VSb （001） film surfaces and its interfaces with GaSh （001） have been investigated within the framework of the density functional theory using the FPLAPW＋lo approach. The NiAs structure is more stable than the ZB phase, ZB VSb is found to a half-metallic ferromagnetic. The V-terminated surfaces retain the half-metallic character, while the half-metallicity is destroyed for Sb-terminated surfaces due to surface states, which originate from p electrons. The phase diagram obtained through the ab-initio atomistic thermodynamics shows that the formation energy of ZB VSb is about 0.1 Ryd. The half-metallicity character is also preserved at VSb/GaSb （001） interface. The conduction band minimum （CBM） of VSb in the minority spin case lies about 0.47 eV above that of GaSb, suggesting that the majority spin can be injected into GaSb without being flipped to the conduction bands of the minority spin.     

Atomic Layer Deposition of Al2O3 on H-Passivated GeSi： Initial Surface Reaction Pathways with H/GeSi（100）-2 × 1

The reaction mechanisms of Al（CH3 ）3 （TMA） adsorption on H-passivated GeSi（100）-2 × 1 surface are investigated with density functional theory. The Si-Ge and Ge-Ge one-dimer cluster models are employed to represent the GeSi（100）-2 × 1 surface with different Ge compositions. For a Si-Ge dimer of a H-passivated SiGe surface, TMA adsorption on both Si-H^＊ and Ge-H^＊ sites is considered. The activation barrier of TMA with the Si-H^＊ site （1.2eV） is higher than that of TMA with the Ge-H^＊ site （0.91 eV）, which indicates that the reaction proceeds more slowly on the Si-H^＊ site than on the Ge-H^＊ site. In addition, adsorption of TMA is more energetically favorable on the Ge-Ge dimer than on the Si-Ge dimer of H-passivated SiGe.     

Density-functional study of CO adsorbed on RhN （N = 2-19） clusters

We investigate the structural, electronic and adsorption properties of one single CO molecule adsorbed on Rh_N (N = 2-19) clusters, using the density-functional theory in the spin-polarized generalized gradient approximation. It is found that the structural growth model of the Rh_N clusters transforms from double layers (N = 12-16) to three layers (N = 17-19). Three different adsorption types are the atop site adsorption for N = 6, 8, 9, 11, 12, the bridge site adsorption for N = 2-5, 7, 10, 13-15, 17 and the face adsorption for N = 16, 18, 19. The adsorption abilities of Rh_N clusters are related to C-O bond length, vibrational frequency, adsorption energy and the charge transfer between CO and Rh clusters as well as the electronic density of state. With the increase of Rh cluster size, the adsorption energy of CO adsorbed on Rh_N clusters tends to be 2.2 eV-2.3 eV, which is 0.2 eV-0.3 eV larger than the theoretical value (about 2.0 eV) of CO molecule adsorption on clean Rh (111) surface.     

Density Functional Calculation of the 0.5ML-Terminated Allyl Mercaptan/Si（100）-（2 × 1） Surface

The structural and electronic properties of the 0.5 ML-terminated allyl mercaptan （ALM）/Si（IO0）-（2 x 1） surface are studied using the density functional method. The calculated absorption energy of the ALM molecule on the 0.5 ML-terminated ALM/Si（IO0）-（2 x 1） surface is 3.36eV, implying that adsorption is strongly favorable. The electronic structure calculations show that the ALM/Si（IO0）-（2 x 1）, the clean Si（100）-（2 x 1）, and the fully-terminated H/Si（IO0）-（2 ~ 1） surfaces have the nature of an indirect band gap semiconductor. The highest occupied molecular orbital is dominated by the ALM, confirming the mechanism proposed by Hossain for its chain reaction.     

Structural Stabilities of Ordered Arrays of Nb4 Clusters on NaCI（IO0） Surface

Adsorption of ordered （2 × 2） arrays of Nb4 clusters on the insulating surface of NaCI（100） is studied by the first-principles calculations within the density functional theory. The calculations on the relaxed geometries and cohesive energies show that both the tetrahedron and quadrangle-Nb4 can be stably adsorbed on this substrate, which may have important applications. The adsorption of quadrangle-Nb4 on the NaCl（100） surface is more stable than that of tetrahedron-Nb4. Both the Nb4 clusters studied and a single Nb atom prefer the top site of the Cl atom in the NaCl（100） surface. Electronic structure analysis suggests that the interactions between the Nb4 clusters and the substrate are weak.     

Surface Structure and Electronic Property of InP（001）-（2×1）S Surface： A First-Principles Study

The surface structure and electronic property of InP（001）-（2 ×1）S surface under S-rich condition are investigated based on first-principles simulations. The analyses of phase transition show that the 3B model is the most stable structure and the S-S dimer is difficult to form. The geometry of the 3B structure agrees well with the experiments. It is also found that the 3B structure has a good passivation with a band gap of about 1.24eV. The results indicate that the 3B structure is the best candidate for the sulfur-rich InP（001）（2 × 1）A phase.     

Methane adsorption on graphite（0001） films： A first-principles study

Using first-principles methods, we have systematically investigated the electronic density of states, work function, and adsorption energy of the methane molecule adsorbed on graphite(0001) films. The surface energy and the interlayer relaxation of the clean graphite(0001) as a function of the thickness of the film were also studied. The results show that the interlayer relaxation is small due to the weak interaction between the neighboring layers. The one-fold top site is found most favourable on substrate for methane with the adsorption energy of 133 meV. For the adsorption with different adsorption heights above the graphite film with four layers, the methane is found to prefer to appear at about 3.21 A above the graphite. We also noted that the adsorption energy does not dependent much on the thickness of the graphite films. The work function is enhanced slightly by adsorption of methane due to the slight charge transfer from the graphite surface to the methane molecule.     

H2S、HCN、PH3在FeO（100）表面吸附的密度泛函理论研究

基于密度泛函理论研究了H2S、HCN、PH3 在FeO(100)表面的吸附行为,其吸附位点主要考虑四个：Fe-top(铁顶位)、O-top(氧顶位)、Hollow(空位)、Bridge(桥位)。结果表明H2S吸附在O-top吸附位点的吸附能最小,为-1.02ev,即在该位点的吸附体系最稳定。当HCN吸附在FeO(100)表面时,各吸附位点的稳定顺序为Hollow>Fe-top>Bridge>O-top。PH3 的最稳定的吸附位点与H2S的一致,为O-top吸附位点,其吸附能为-1.11ev。当H2S吸附在O-top吸附位点时,H2S与FeO（100）表面的电荷转移量最多,说明该吸附构型最稳定,而HCN吸附在FeO(100)表面,在Hollow吸附位点的电荷转移量最多,也即该吸附位点属于最稳定吸附位点。PH3与FeO（100）表面之间的电荷转移量最多的吸附位点与H2S的相同。当H2S和PH3吸附在O-top吸附位点时,吸附后的态密度曲线整体向低能级移动,峰值降低,其吸附结构变得更加稳定。而HCN吸附在Hollow位点时,吸附后的HCN态密度曲线向能量更低的区域移动,吸附体系变得更稳定。     

Dissociative Chemisorption of an H2（v,j） Molecule on Rigid Ni （100） Surface： Dependence on Surface Topologies and Initial Rovibrational States of the Molecules

The H2(v,j) Ni(100) collision system has been studied to understand the effects of the surface sites and initial rovibrational states of the molecule on molecule-surface interactions, by a quasiclassical molecular dynamic simulation method. Dissociative adsorption of an H2 molecule on the rigid Ni(100) surface is investigated at topologically different three sites of the surface. Interaction between the molecule and Ni surface was described by a London-Eyring-Polani-Sato (LEPS) potential. Dissociative chemisorption probabilities of the H2(v, j) molecule on various sites of the surface are presented as a function of the translation energies between 0.001-1.0eV. The probabilities obtained at each collision site have unique behaviour. At lower collision energies, indirect processes enhance the reactivity, effects of the rotational excitations and impact sites on the reactivity are more pronounced. The results are compared with the available studies. The physical mechanisms underlying the results and quantum effects are discussed.     

Spin Polarization Properties of Na Doped Meridianal Tris（8-Hydroxyquinoline） Aluminum Studied by First Principles Calculations

We theoretically investigate the electronic structure and spin polarization properties of Na-doped meridianal tris（S-hydroxyquinoline） aluminum （Alq3） by first principles calculations. It is found that the spin density is distributed mainly in the Alq3 part in the Alq3：Na complex. Electron charge transfer takes place from the Na atom to the Alq3 molecule, which induces asymmetric changing of the molecule bond lengths, thus the spin density distribution becomes asymmetric. Spin polarization of the complex originates from the preferable filling of the spin-split nitrogen and carbon p-orbitals because of the different bond length changes of the Aiq3 molecule upon Na doping.     

First-principles study on anatase TiO2（101） surface adsorption of NO

In this paper, the stable structure and the electronic and optical properties of nitric oxide （NO） adsorption on the anatase TiO2 （101） surface are studied using the plane-wave ultrasoft pseudopotential method, which is based on the density functional theory. NO adsorption on the surface is weak when the outermost layer terminates on twofold coordinated oxygen atoms, but it is remarkably enhanced on the surface containing O vacancy defects. The higher the concentration of oxygen vacancy defects, the stronger the adsorption is. The adsorption energies are 3.4528 eV （N end adsorption）, 2.6770 eV （O end adsorption）, and 4.1437 eV （horizontal adsorption）. The adsorption process is exothermic, resulting in a more stable adsorption structure. Furthermore, O vacancy defects on the TiO2 （101） surface significantly contribute to the absorption of visible light in a relatively low-energy region. A new absorption peak in the low-energy region, corresponding to an energy of 0.9 eV, is observed. However, the TiO2 （101） surface structure exhibits weak absorption in the low-energy region of visible light after NO adsorption.     

Influence of High Atomic Hydrogenation on the Electronic Structure of Zigzag Carbon Nanotubes： A First-Principles Study

Using density functional theory, we study high hydrogenated zigzag single-walled carbon nanotubes from （7,0） to （11,0）. Two structure transitions are classified： type A is a metallic transition and type B is a ＂semiconductive transition＂ according to the energy band structure. The charge density transforms only at the C-C bonds without hydrogenated sites. The sp^3 hybridization is mainly enhanced for all the C-C bonds in the vertical axial direction for type-A configurations, and the sp^3 hybridization mainly increases for all C-C bonds along the axial direction for the type-B case.     

Bulk Modulus and Electronic Band Structure of ZnGa2Xa （X=S,Se）： a First-Principles Study

First-principles local density functional calculations are presented for the compounds ZnGa2X4 （X = S, Se）. We investigate the bulk moduli and electronic band structures in a defect chalcopyrite structure. The lattice constants and internal parameters are optimized. The electronic structures are analysed with the help of total and partial density of states. The relation between the cohesive energy and the unit cell volume is obtained by fully relaxed structures. We derive the bulk modulus of ZnGa2Xa by fitting the Birch-Murnaghan＇s equation of state. The extended Cohen＇s empirical formula agrees well with our ab initio results.