Augmented Wave Method Research Articles

Tuning the electronic property of monolayer MoS2 adsorbed on metal Au substrate: a first-principles study

Using first principles calculations within density functional theory, we investigate the electronic property of a single-layer MoS2 adsorbed on Au. All the quantities are calculated using the Vienna ab initio simulation package. Calculations are performed using the projector augmented wave method with the Perdew-Burke-Ernzerhof functional and a kinetic energy cutoff of 400 eV. The atomic plane and its neighboring image are separated by a 15 Å vacuum layer. The k-meshes for the structure relaxation and post analysis are 9×9×1 and 19×19×1, respectively. The spin-orbit coupling is considered in the calculation. The research includes the binding energy, the band structure, density of states (DOS) and electric charge difference density. Three contact modes between MoS2 (0001) and Au (111) are considered. When the atom S layer and the atom Au layer on the contacting interface have the same structure, the minimum binding energy and distance between MoS2 (0001) and Au(111) are 2.2 eV and 2.5 Å respectively. The minimum binding energy confirms that the absorption is unstable. The band structure demonstrates that the MoS2-Au contact nature is of the Schottky-barrier type, and the barrier height is 0.6 eV which is bigger than MoS2-Sc contact. By comparison with other metal contacts such as Ru(0001), Pd(111) and Ir(111), the dependence of the barrier height on the work function difference exhibits a Fermi-level pinning. But the MoS2 is so thin that the Fermi-level pinning must be very small. Maybe there is a metal induced gap state. DOS points out that the Au substrate has no influence on the covalent bond between Mo and S. The influence of the Au substrate is that it shifts the DOS of monolayer MoS2 left on the axis. The change of DOS results in the increases of electron concentration and electric conductivity. Other calculation points out that Ti substrate can excite more electrons. Electric charge density difference demonstrates that there are a few electric charges that transfer on the contact interface. The conducting path of monolayer MoS2 may emerge at the interface between Au and MoS2. In summary, the Au electrode is not the best electrode in the MoS2 device. The Ti electrode can excite more electrons from MoS2. The work function of Sc electrode is close to the affine of MoS2. The Fermi energy level of graphene can be tuned by external voltage. So the Ti, Sc and graphene will be the better electrodes for MoS2 device. Results of this study may provide a theoretical basis for single-layer MoS2 transistor and guidance for its applications.

First-principles study of effects of quantum confinement and strain on the electronic properties of GaSb nanowires

Using first-principles calculations based on density functional theory and projector augmented wave method, we investigate the electronic structures of one-dimensional wurtzite (WZ) and zinc-blende (ZB) GaSb nanowires with different diameters along the [0001] and [111] directions, respectively. The results show that the band gap of the GaSb nanowire increases as the size of the nanowire decreases due to the quantum confinement, and the band structures of the GaSb nanowires display an indirect band structures feature when the diameter of the nanowire is smaller than 3.0 nm, whereas bulk GaSb has a direct gap. Owing to the different responses of the valence band maximum/conduction band minimum energies to strain, the band structures of GaSb nanowires experiences a noticeable indirect-to-direct transition when the nanowires are under the uniaxial strain. For example, an indirect-to-direct band gap transition in the band structure of [111] ZB GaSb nanowires can be realized by applying a uniaxial tensile strain, and this transition in the band structure of [0001] WZ GaSb nanowires can take place by applying both uniaxial tensile and compression strain when the diameter of the nanowire is about 2.0 nm. In addition, it is found that carrier effective mass is dependent on the diameter of the GaSb nanowire, therefore both the electron and hole effective mass values decrease as diameter increases. It is also found that the hole effective mass is smaller than the electron effective mass for GaSb nanowires with the same directions and sizes, indicating that the hole transportation is more prominent than the electron transportation.

Structural phase transition, electronic structures and optical properties of ZnTe

The equations of state and phase transition of ZnTe in zinc blende (ZB) and cinnabar (CB) structures under high pressure are investigated by the projected augmented wave method in the scheme of density functional theory. The primitive cell volumes, electronic structures and optical properties are also predicted before and after phase transition. The variations of the calculated total energy with volume, for the structures of ZB and CB, yield the information about the static equation of state and phase stability. The results show that the ZB phase of ZnTe has lower energy, and is more stable than its CB phase. The pressure-induced transition occurs along the common tangent line connecting the tangential points on the two enthalpy-volume curves. The calculations show that the phase transition pressure is 8.6 GPa from the ZB structure to the CB structure. The value is also compatible with those of other available theoretical and experimental results. Just before the ZB phase is transferred to the CB phase at about 8.6 GPa, the volume is reduced by 13.0% relative to the former volume at the ambient pressure condition. The calculated critical volumes and volume compressibilities by using two methods agree well with other results in the literature. The lattice parameters and equations of state of the two structures are also obtained. Metallization case of other similar materials such as ZnS caused by high pressure does not occur here. The CB phase has the behavior of indirect band gap with 0.98 eV along the symmetry of GK. After phase transition, the distributions of density of states of Zn and Te atoms of the CB structure shift towards lower energy, especially in the conduction band bottom, and the band gap decreases. Energy level overlapping is more obvious in the CB structure, and orbital hybridizations still exist, that is the reason why it is the stable phase under high pressure condition. Stronger orbital hybridization helps the transitions between Te 5p and Zn 3d electrons. The main peak of imaginary part of dielectric constant is enhanced apparently with abnormal red shift, while other two peaks disappear at the same time. Macroscopic dielectric constant of ZB structure decreases as pressure increases. For CB structure, the macroscopic dielectric constant with 13.60 eV is not affected by pressure. The results provide a theoretical basis for the polarization research of ZnTe material in static electric field under high pressure.

First-Principles Calculations and Analysis of29Si Nuclear Magnetic Resonance Chemical Shifts in Silicon Oxycarbide Ceramics

We calculate 29Si NMR chemical shifts for silicon atoms in different chemical environments observed in amorphous silicon oxycarbide ceramics using a library of optimized structural models and the gauge-including projector augmented wave (GIPAW) method. For each type of mixed tetrahedral environment, {Si}O4, {Si}O3C, and {Si}O2C2, we develop linear angular correlation functions that relate the 29Si NMR shift of the central silicon atom to the Si–O–Si angles surrounding it. The bonding nature of carbon atoms, whether 4-fold (sp3) or 3-fold (sp2) connected, impacts the chemical shift of {Si}O3C units and can be used to distinguish between Si–C bonding in the “glassy” SiCO host structure and at the interface to so-called “free” carbon. With the derived correlation functions, we analyze two representative experimental 29Si NMR spectra and extract their angle distributions. Our results are in agreement with X-ray and neutron diffraction data. Probing for an interface between “free” carbon and “glassy” SiCO host in a C-rich SiCO material, we find no evidence of significant bonding between Si and three-connected (sp2) C. Rather, the material exhibits a large fraction of wide Si–O–Si angles, which are typical of cage-like and zeolitic structures.

Hydrides of YPd3: Electronic structure and dynamic stability

Ternary intermetallic YPd3 is known to exhibit superior hydrogen storage capacity compared to pure palladium. To understand the characteristics of YPd3 on hydrogenation, the ground state electronic and dynamical properties were computed by two computational methods, the full potential linearized plane wave and projector augmented wave methods within the density functional theory. Hydrogen can be inserted in YPd3 at various octahedral sites, giving rise to model structures YPd3H and YPd3H4 which retain the L12 crystal structure. The calculated energy bands confirm the metallic nature of YPd3 and also exhibit greater dispersion of bands with increase in hydrogen content. Large variations in the optical constants such as transmittance is observed (by ∼40% in the violet region) with insertion of hydrogen, YPd3 may have thus have applications as a sensing device for monitoring hydrogen for using hydrogen safely. The electronic component γ obtained from the temperature dependent specific heats, is related to the density of states at the Fermi level which may be co-related to instability of hydrides.The modes at Γ-point in YPd3H and at X and M-points in YPd3H4 give rise to high peaks in the imaginary frequency regime which could drive the dynamical instabilities. From the formation energies and phonon modes it is found that the monohydride YPd3H is more stable, thus occupation of the octahedral sites at 2Y4Pd by hydrogen atoms results in greater dynamic instability in YPd3.

Analysis of electronic structure of boron nitride nanotubes with different positions of intrinsic impurities

The pristine boron nitride nanotubes have a large direct band gap around 5 eV. This band gap can be engineered by doping. We investigate electronic structure of the doped hexagonal boron nitride (5,5) nanotubes using the linearized augmented cylindrical wave method. In particular, this work focuses on systematical study of the band gap and the density of states around the Fermi-level when the nanotubes are doped by intrinsic impurities of two substitutional boron atoms in a super cell and a comparative analysis of the relative stability of three structures studied here. This corresponds to 3.3% of impurity concentration. We calculate 29 configurations of the nanotubes with different positions of the intrinsic impurities in the nanotube. The band gap and density of states around the Fermi level show strong dependence on the relative positions of the impurity atoms. The two defect sub bands called Dπ(B) appear in the band gap of the pristine nanotube. The doped nanotubes possess p-type semiconductor properties with the band gap of 1.3-1.9 eV.

Computing total energies in complex materials using charge self-consistent DFT + DMFT

We have formulated and implemented a fully charge self-consistent density functional theory plus dynamical mean-field theory methodology which enables an efficient calculation of the total energy of realistic correlated electron systems. The density functional portion of the calculation uses a planewave basis set within the projector augmented wave method enabling study of systems with large, complex unit cells. The dynamical mean-field portion of the calculation is formulated using maximally localized Wannier functions, enabling a convenient implementation which is independent of the basis set used in the density functional portion of the calculation. The importance of using a correct double-counting term is demonstrated. A generalized form of the standard double-counting correction, which we refer to as the ${U}^{\ensuremath{'}}$ form, is described in detail and used. For comparison, the density functional plus $U$ method is implemented within the same framework including the generalized double counting. The formalism is validated via a calculation of the metal-insulator and structural phase diagrams of the rare-earth nickelate perovskites as functions of applied pressure and A-site rare-earth ions. The calculated density functional plus dynamical mean-field results are found to be consistent with experiment. The density functional plus $U$ method is shown to grossly overestimate the tendency for bond disproportionation and insulating behavior.

First principles studies of GeTe based dilute magnetic semiconductors

The electronic structure and magnetic properties of GeTe-based dilute magnetic semiconductors (DMS) are investigated by the Korringa–Kohn–Rostoker Green's function method and the projector augmented wave method. Our calculations for the formation energies of transition metal impurities (TM) in GeTe indicate that the solubilities of TM are quite high compared to typical III–V and II–VI based DMS and that the TM doped GeTe has a possibility of room temperature ferromagnetism with high impurity concentrations. The high solubilities originate from the fact that the top of the valence bands of GeTe consists of the Te-5p anti-bonding states which are favorable to acceptor doping. (Ge, Cr)Te system shows strong ferromagnetic interaction by the double exchange mechanism and is a good candidate for DMS with high Curie temperature. Additionally, in the case of (Ge, Mn)Te with the d5 configuration, by introducing the Ge vacancies the p-d exchange interaction is activated and it dominates the antiferromagnetic superexchange, resulting in ferromagnetic exchange interactions between Mn. This explains recent experimental results reasonably. Based on the accurate estimation of the Curie temperatures by Monte Carlo simulation for the classical Heisenberg model with the calculated exchange coupling constants, we discuss the relevance of the TM doped GeTe for semiconductor spintronics.

NMR characterization of hydrocarbon adsorption on calcite surfaces: a first principles study.

The electronic and coordination environment of minerals surfaces, as calcite, are very difficult to characterize experimentally. This is mainly due to the fact that there are relatively few spectroscopic techniques able to detect Ca(2+). Since calcite is a major constituent of sedimentary rocks in oil reservoir, a more detailed characterization of the interaction between hydrocarbon molecules and mineral surfaces is highly desirable. Here we perform a first principles study on the adsorption of hydrocarbon molecules on calcite surface (CaCO3 (101¯4)). The simulations were based on Density Functional Theory with Solid State Nuclear Magnetic Resonance (SS-NMR) calculations. The Gauge-Including Projector Augmented Wave method was used to compute mainly SS-NMR parameters for (43)Ca, (13)C, and (17)O in calcite surface. It was possible to assign the peaks in the theoretical NMR spectra for all structures studied. Besides showing different chemical shifts for atoms located on different environments (bulk and surface) for calcite, the results also display changes on the chemical shift, mainly for Ca sites, when the hydrocarbon molecules are present. Even though the interaction of the benzene molecule with the calcite surface is weak, there is a clearly distinguishable displacement of the signal of the Ca sites over which the hydrocarbon molecule is located. A similar effect is also observed for hexane adsorption. Through NMR spectroscopy, we show that aromatic and alkane hydrocarbon molecules adsorbed on carbonate surfaces can be differentiated.

Theoretical study of electronic structure, phase transition, elastic, and thermodynamic properties of ReN

Phase transition of rhenium mononitride (ReN) in NaCl, CsCl, zincblende (ZB), NbO, wurtzite (WZ), NiAs, WC, PtS, Pmn21 and Cmc21 structures have been studied by using the projector augmented wave method. It is found that NbO-type structure is the most stable. This conclusion is consistent with the report of Wang et al., while contrary to the results of Zhao et al., Chen et al., Asvini et al., and Hlynsson et al. The phase transition from NbO-type to NiAs-type occurs at ca. 52.8GPa, which is also in good agreement with that of Wang et al. The elastic constants of NbO- and NiAs-type ReN under high pressure are calculated and found to be increased with the increasing pressures. At the same time, the ductile-brittle behavior is evaluated by Pugh's criteria. Also, we have predicted the density of states and Vickers hardness for NbO and NiAs types of ReN. Finally, the Debye temperature ΘD, thermal expansion α and heat capacity CV for NbO-type structure at high pressures are also derived through the quasi-harmonic Debye model.

Substitutional impurities influence on hydrogen sorption properties of titanium and zirconium

The influence of substitutional impurities on the hydrogen absorption energy in Ti and Zr is investigated by the projector augmented wave method within the density functional theory. Obtained results demonstrate that simple metal atoms are repulsive to H, whereas transition metal atoms attract H and provide traps for H. The relationship between the interaction energy, the lattice distortion and the electronic structure of metals is analyzed.

Site preference of Hf dopant in Ni3Al alloys: A perturbed angular correlation study

Perturbed angular correlation measurements of the hyperfine interactions of the 181Ta probe in the polycrystalline intermetallic Ni3Al doped with 0.5 and 5at.% Hf were performed in the temperature range 78–1230K. The observed local hyperfine fields at the 181Hf/181Ta probe showed that Hf atoms are substituting on Al sites in the L12 structure of Ni3Al. The two minor electric quadrupole interactions that were found for each Ni3Al alloy are discussed taking into account the L12 cubic structure and its two tetragonal distortions: D022 and L60. The presence of two tetragonal transformations of the parent cubic L12 lattice in 0.5at.% Hf and 5at.% Hf doped Ni3Al was revealed by X-ray diffraction. The ab initio calculations, performed with the projector augmented wave method correctly reproduce the experimental results and enable discussion on the structural and electronic properties of the polycrystalline alloys. The experimental and theoretical investigations showed that hafnium additions prefer aluminum sites in Ni3Al.

Ab initio investigations of electron correlation effect and phonon dynamics of orthorhombic uranium

We have performed first principles calculations for the electronic, dynamical, and thermodynamic properties of α‐U using the projector augmented wave (PAW) method. The optimized lattice parameters, equilibrium volume, atomic energy, bulk modulus, and its pressure derivative are close to the experimental data and other calculations. To evaluate the strong on‐site Coulomb repulsion among the localized uranium 5f electrons, the generalized gradient approximation (GGA)+U formalism have been adopted. It is shown that the total DOS at the Fermi energy level mainly comes from the contribution of narrow f band, the electron correlation effect is small for metallic bands of uranium. In particular, the phonon spectrum of α‐U is calculated within density functional perturbation theory (DFPT) as well as the small displacement method, the coincidence between our calculations and Crummett et al.'s inelastic neutron scattering measurements indicates that both phonon methods based on PAW scheme are reasonable to capture the anomalous phonon properties of α‐U. The calculated dynamical properties of uranium under pressure suggest that Cmcm uranium should be stabilized dynamically at least up to 100 GPa, which accords with X‐ray diffraction experimental results of Le Bihan et al. The thermodynamic functions of α‐U under high temperature and high pressure are also obtained further.

ChemInform Abstract: Deformation Induced Solid—Solid Phase Transitions in Gamma Boron.

AbstractThree new polymorphs of boron are predicted by applying DFT (Perdew—Burke—Ernzerhof) calculations using the projector augmented wave method to large shear deformations starting from the recently discovered γ‐B28 boron phase (stable above 9 GPa and 1000 K).

Electroconductive properties in doped spinel oxides

The application of spinel oxides as transparent conducting oxides (TCOs) in optoelectronic devices as a substitute for ZnO is attracting attention in the recent years. Despite attractive photo-luminescence properties of zinc aluminate and zinc gallate, relatively little work has been done to interpret the optical response of spinel oxides on the basis of energy band structures. We present the electronic properties of ZnX2O4 (X=Al, Ga, In) calculated by the full potential linearized augmented plane wave method. Optical properties such as absorption coefficient and reflectivity are calculated and interpreted in terms of energy bands and density of states. Enhancement in optical properties was studied for Li and Mn ions doped in the ZnGa2O4 matrix. The main features in the experimentally observed photoluminescence spectra for doped and undoped ZnGa2O4 have been verified through the optical parameters.The transparence of spinel oxides to UV radiations is also clearly illustrated in the reflectivity vs. energy curves. At very small wavelengths the oxides may be used as reflective coating materials. Transport properties of the zinc spinel oxides have been investigated for the first time, and are found to have high Seebeck coefficients, high electrical conductivity and low thermal conductivity, with high value of figure of merit ZT∼0.8. The study of vibrational and thermodynamic properties by the projector augmented wave method confirms the dynamic stability of the doped and undoped spinel oxides. Zinc spinel oxides are found to be p-type semiconductors with an optimum value of band gap ∼2–3eV and appear to meet the conditions of low resistivity and high transparency (>80%) for state-of-art TCOs.

Deblocking effect of carbonates and hydrogen carbonates in the alkali form zeolites with narrow pores

The alkali forms of MeRHO zeolite (Me=Li, Na, K, Cs) are studied theoretically at the DFT/PBE level using projector augmented wave method (PAW) and periodic boundary conditions (PBC). The equilibrium positions of the Me cations have been optimized at the D8R prisms where they control molecular transport in the pores of MeRHO. The effect of the displacement of alkali cations has been estimated due to coordination of both carbonate or hydrogen carbonate anions that can also induce RHO framework transformations. Admitting the CO3−2 and HCO3− formations via the reactions between H2O and CO2, the energy of respective reactions was evaluated at various Si/Al moduli and analyzed regarding possible influence on the gas adsorption.

PredictiveGWcalculations using plane waves and pseudopotentials

We show that quasiparticle (QP) energies as calculated in the $GW$ approximation converge to the wrong value using the projector augmented wave (PAW) method, since the overlap integrals between occupied orbitals and high energy, plane wave like orbitals, are incorrectly described. The error is shown to be related to the incompleteness of the partial wave basis set inside the atomic spheres. It can be avoided by adopting norm-conserving partial waves, as shown by analytic expressions for the contribution from unoccupied orbitals with high kinetic energy. Furthermore, $G_0W_0$ results based on norm-conserving PAW potentials are presented for a large set of semiconductors and insulators. Accurate extrapolation procedures to the infinite basis set limit and infinite k-point limit are discussed in detail.

Oxygen Reduction Reaction Sites and Electron Conduction Mechanism of Zr-Oxide-Based Catalyst:Soft X-Ray SR-XPS and First-Principles Calculations

Polymer electrolyte fuel cells (PEFCs) have expected as one of the key energy devices in future sustainable society. PEFCs, however, have difficult issues such as insufficient oxygen reduction reaction (ORR) activity and expensive Pt consumption. To overcome such difficulties, various non-platinum ORR catalysts, such as, carbide, nitride, and oxide were examined as alternative of Pt [1]. Among them, Zr oxide-based catalysts attract much attention. Such transition-metal-oxide catalysts show the high ORR onset potentials, but ORR current is very low. Thus, identifying the ORR sites, and designing surface structure to have effective ORR sites, is mail issues in developing oxide-base catalysts.Previously, we reported that oxygen-vacancy sites could be ORR sites by surface-sensitive conversion-electron-yield x-ray absorption spectroscopy (CEY-XAS) [2]. But we still lack detailed information on preferable electronic structure of oxide-base ORR catalyst. Since carbon is deposited at catalysts surface during partial oxidation preparation processes, conventional laboratory XPS does not provide effective information, especially at valence band (V.B.) region. Thus, we conducted highly brilliant soft X-ray synchrotron radiation (SR)-XPS measurements. First-principles calculation was adopted to interpret the partial density of state (PDOS) of V. B.ZrO2 based catalyst samples were prepared under O2 and H2/N2 atmosphere from Zr- phthalocyanine. The SR-XPS measurements were performed on BL-18A beam line at Photon Factory (PF) of High Energy Accelerator Research Organization (KEK). PDOS calculation was carried out by using the plane-wave basis projected augmented wave (PAW) method (VASP) [3].Figure 1 (a) shows the soft x-ray SR-XPS spectra of ZrO2 reference. Each spectrum was obtained after subtracting the spectrum measured at 31 eV X-ray energy. We can see that peak intensity at 4 to 8 eV regions were increased as incident energy increased, suggesting that these peaks originate from ZrO2. As shown in Fig.1 (b), the SR-XPS spectra of ZrO2 catalyst also show similar trend. This indicates that we can truly observe V.B of catalysts even if a part of surface is covered with carbon. Figure 2 shows the PDOS spectra calculated ZrO2 with oxygen vacancy. The Peak near 4eV can be originated from O 2p. This result suggest reduction of SR-XPS spectral intensity for catalysts compared with reference ZrO2comes from oxygen vacancy in the catalysts, and such O-vacancy should play a role in emergence of ORR activity. Detailed electronic structure consideration will be presented at Meeting. Acknowledgement: A part of this work was performed under the “Non-precious metal oxide-based cathode for PEFC Project” supported by the New Energy and Industrial Technology Development Organization (NEDO). SR-XPS measurements were performed with an approval of High Energy Accelerator Research Organization (Proposal No. 2013P102) .

EPR parameters ofE′centers inv−SiO2from first-principles calculations

A first-principles investigation of ${E}^{\ensuremath{'}}$ centers in vitreous silica $(v\ensuremath{-}{\mathrm{SiO}}_{2})$ based on calculations of the electron paramagnetic resonance (EPR) parameters is presented. The EPR parameters are obtained by exploiting the gauge including projector augmented wave method as implemented in the quantum-espresso package. First, we analyze the EPR parameters of a large number of ${\mathrm{Si}}_{2}$ dimers. The $g$ tensor of the ${\mathrm{Si}}_{2}$ dimers is shown to possess an average rhombic symmetry and larger $g$ principal values with respect to those observed, e.g., for the ${E}^{\ensuremath{'}}$${}_{\ensuremath{\gamma}}$ center in silica. Furthermore, the $g$ principal values clearly show a linear trend with the Si-Si dimer length. Our results suggest that the ${\mathrm{Si}}_{2}$ dimers could correspond to an unidentified paramagnetic center, though occasionally the calculated $g$ principal values of the ${\mathrm{Si}}_{2}$ dimer might be compatible with those found experimentally for the ${E}^{\ensuremath{'}}$${}_{\ensuremath{\delta}}$ center. Next, we generate nondimer configurations by a procedure involving structural relaxations in the subsequent positively charged states. In particular, puckered, unpuckered, doubly puckered, and forward-oriented configurations are generated. The distributions of the calculated EPR parameters of the puckered and unpuckered configurations further support the assignment of the ${E}^{\ensuremath{'}}$${}_{\ensuremath{\gamma}}$ center to an unpaired spin localized at a threefold coordinated silicon dangling bond. Moreover, by analyzing Fermi contacts and $g$ tensors of the puckered and forward-oriented configurations, we suggest the assignment of the ${E}^{\ensuremath{'}}$${}_{\ensuremath{\alpha}}$ center to the latter type of configurations. This work also suggests that the differences in the EPR parameters of ${E}^{\ensuremath{'}}$${}_{\ensuremath{\alpha}}$ and ${E}^{\ensuremath{'}}$${}_{\ensuremath{\gamma}}$ centers mainly arise from the strained geometry of the silicon dangling bond. In the forward-oriented configurations, one Si-O bond is about 0.2 \AA{} longer than the remaining two, whereas in the silicon dangling bond of the puckered and unpuckered configurations, all three bonds have a length of $\ensuremath{\sim}$1.6 \AA{} each.

A first-principles study of Pt–Ni bimetallic cluster adsorption on the anatase TiO 2 (1 0 1) surface: Probing electron effect of Ni in TiO 2 (1 0 1)-bimetallic cluster (Pt–Ni) on the adsorption and dissociation of methanol

Abstract A density functional theory (DFT) based method in conjunction with the projector augmented wave and pseudopotential methods have been applied to investigate the adsorption of Pt4 and Pt3Ni on the anatase TiO2 (1 0 1) surface. Two stable Pt3Ni adsorptions with considerable adsorption energies on the anatase TiO2 (1 0 1) surface were identified. Analysis of the partial density (PDOS) of states and Bader charge suggest that the electronic structure of Pt is modified by Ni due to the electron transfer from Ni to Pt atoms in the Pt3Ni clusters. The 2cO (3cO)-PtNi-5cTi conformation of the adsorbed Pt3Ni on the anatase TiO2 (1 0 1) surface provides a more feasible model for electron injection through the Pt3Ni/TiO2 interface. The reactivity of Pt3Ni/TiO2 is superior to Pt4/TiO2 and effectively manifests itself in the eased decomposition of O H bonds derived by methanol and alleviative CO adsorption.