Perdew , Burke And Ernzerhof Research Articles

Investigation on the electronic structure, optical, elastic, mechanical, thermodynamic and thermoelectric properties of wide band gap semiconductor double perovskite Ba2InTaO6.

In the present paper, double perovskite Ba2InTaO6 was investigated in terms of its structural, electronic, optical, elastic, mechanical, thermodynamic and thermoelectric properties using density-functional theory (DFT). The generalized gradient approximation (GGA) in the scheme of Perdew, Burke and Ernzerhof (PBE) and the modified Becke–Johnson (mBJ) potential were employed for the exchange–correlation potential. The computed lattice constant was found to be in agreement with the available experimental and theoretical results. The electronic profile shows a semiconducting nature. Further analysis of the complex dielectric constant ε(ω), refractive index n(ω), reflectivity R(ω), absorption coefficient α(ω), optical conductivity (ω) and energy loss function were also reported with the incident photon energy. The elastic constants were also calculated and used to determine mechanical properties like Young's modulus (Y), the shear modulus (G), Poisson's ratio (ν) and the anisotropic factor (A). The electrical conductivity (σ/τ) and Seebeck coefficient (S) also demonstrated the semiconducting nature of the compound with electrons as the majority carriers. The value of the power factor was calculated to be 1.20 × 1012 W K−2 m−1 s−1 at 1000 K. From thermodynamic investigations, the heat capacity and Grüneisen parameter were also predicted.

Electronic exchange-correlation, many-body effect issues on first-principles calculations of bulk SiC polytypes

The first-principles Projector-Augmented Wave method (PAW) is used to investigate the electronic, phonon band structure and dielectric properties of four bulk silicon carbide (SiC) polytypes. We employ PAW pseudopotential density functional theory with Perdew, Burke and Ernzerhof (PBE) and hybrid HSE06 approximations of the exchange-correlation functional. Many-body effects are incorporated using the GW approximation of the self-interaction to study SiC properties. GW method in its single-shot variant, which is based on the many-body perturbation theory (MBPT), is used to calculate the quasi-particle (QP) energies of the band structure and the dielectric properties for different polytypes. The electronic band structure determination within GW method uses the Wannier procedure where a basis set of maximally localized Wannier function (MLWF) is constructed to interpolate the QP energies of few regular mesh k-points to the high-symmetry lines in Brillouin zone. As a consequence of QP correction to the Kohn–Sham energies, bandgap is increased by upto 3 eV in case of 4H–SiC, as compared to PBE bandgap. GW results are comparable to those of hybrid functionals and are in good agreement with the experimental results. The optical properties are then studied within PBE, HSE06 and include many-body effects. In addition, the phonon band structure has been investigated within HSE06 and compared to previous PBE results. We found good agreement with the previous theoretical results and the experimental available data.

First principles study of structural and electronic properties of BNNTs

In this article the electronic and structural properties of single-walled boron nitride (BN) nanotubes with a diameter range of 4–22 A have been investigated using the generalized gradient approximation with both Perdew, Burke and Ernzerhof (PBE) and Becke–Lee–Yang–Parr (BLYP) functionals based on density functional theory. The variation of radial distribution, bond length, lattice constant, density of states, buckling separation, total energies and the electronic band gap of BN nanotubes have been studied in terms of the diameter of the nanotube. Our results revealed a correlation between the buckling and band gap: the higher the buckling, the lower the band gap, and by decreasing the tube diameter, the buckling separation increases. It is revealed that for both armchair and zigzag boron nitride nanotubes (BNNT) the value of the band gap increases by increasing the nanotube diameter. Moreover, it is concluded that for small BN nanotubes by reducing the radius, the band gap of the armchair nanotube remains almost constant, while the band gap of the zigzag nanotubes has a rapidly decreasing trend. The value of band gap obtained by the BLYP hybrid functional is more accurate than the PBE functional. The PDOS calculations revealed that the VBM comes from the N 2p orbitals, while the CBM is ruled by the B 2p orbitals. According to the obtained results, BNNTs are suggested as good materials for applications in the nanoscale optoelectronic devices.

CHD3 dissociation on Pt(111): A comparison of the reaction dynamics based on the PBE functional and on a specific reaction parameter functional

We present a comparison of ab initio molecular dynamics calculations for CHD3 dissociation on Pt(111) using the Perdew, Burke and Ernzerhof (PBE) functional and a specific reaction parameter (SRP) functional. Despite the two functionals predicting approximately the same activation barrier for the reaction, the calculations using the PBE functional consistently overestimate the experimentally determined dissociation probability, whereas the SRP functional reproduces the experimental values within a chemical accuracy (4.2 kJ/mol). We present evidence that suggests that this difference in reactivity can at least in part be attributed to the presence of a van der Waals well in the potential of the SRP functional which is absent from the PBE description. This leads to the CHD3 molecules being accelerated and spending less time near the surface for the trajectories run with the SRP functional, as well as more energy being transferred to the surface atoms. We suggest that both these factors reduce the reactivity observed in the SRP calculations compared to the PBE calculations.

First-Principles Study of Catalytic Activity of Cu, Ni and Pd Surface for Formaldehyde and Hypophosphite As Reducing Agents in Electroless Deposition

Electroless deposition process has been applied to various industrial fields as a fundamental technique to fabricate metal thin films. To improve the controllability of this process, investigations of the reaction mechanism and the catalytic activity of metal surfaces for each reducing agent reaction are essentially important. For systematic analyses, theoretical calculation can be employed as a powerful tool. Our previous theoretical studies suggested that the dehydrogenation step of the reducing agents could be a rate-determining step in most cases [1]. This study investigates the reaction mechanisms of reducing agents with solvent molecules on Cu, Ni, and Pd, analyzing the electronic states during the reaction to identify the origin of the catalytic activity observed in each metal surface, by using density functional theory (DFT). All calculations were performed by using Vienna Ab initio Simulation Package (VASP). The cutoff energy for the plane wave basis set was set at 400 eV. The core electrons were described by pseudopotentials constructed with the Projector Augmented Wave (PAW). The exchange-correlation energies were evaluated with the Perdew, Burke and Ernzerhof (PBE) functional. The k-point grids were taken as 3 × 3 × 1 for the geometry optimization and 15 × 15 × 1 for the density of states (DOS) calculations. Assuming that the process employs high pH solution, the molecular structures of formaldehyde and hypophosphite ions were modeled as H2CO(OH)- and H2PO2 -, respectively. The solvation structures were prepared by locating several explicit H2O molecules, which were directly interacting with the molecules of the reducing agents. Previous study of each elementary step, such as the adsorption and the dehydrogenation, indicated that H2O played an important role to determine the geometrical structure or electronic state in those steps. To obtain a reasonable result of the solid-liquid interface system, the solvation structures of each reducing agent were investigated. H2O molecules turned out to interact mainly with O atoms of formaldehyde via H atoms in the solvation structure (Fig. 1), which was almost the same as the case of hypophosphite. Due to the sterically bulky structure around O atoms, the two reducing agent molecules adsorbed on each metal surface via H atoms; H and center atoms locate on atop and bridge sites, respectively. The solvation structure prevented unreasonable dissociation of the molecules on metal surfaces, suggesting that the surrounding solvent molecules are necessary to build the practical adsorption model. The reaction energies of the dehydrogenation on each metal surface have good agreement with the catalytic activity shown in the experimental results [2]. DOS profiles demonstrate that the electronic state of the dissociated H atom of formaldehyde is sufficiently stabilized by the effective interaction with Cu surface atom, while that of hypophosphite is not. Such a detailed investigation for the electronic state of the reducing agents at each surface during the reaction is helpful to elucidate their reactivity. [1] M. Kunimoto, T. Shimada, S. Odagiri, H. Nakai, T. Homma, J. Electrochem. Soc., 158, D585-D589 (2011). [2] I. Ohno, O. Wakabayashi, S. Haruyama, J. Electrochem. Soc., 132, 2323-2330, (1985). Figure 1

The structure of water – Acetamide hydrogen bonded complexes. Quantum chemical analysis

The structure of acetamide dimers and hydrogen-bonded complexes of acetamide with water molecules (1–4 molecules in the complex) have been studied by quantum chemical method on the base of density functional theory (DFT) approximation using hybrid Becke, three-parameter, Lee-Yang-Parr (B3LYP) functional and gradient-corrected correlation functional of Perdew, Burke and Ernzerhof (PBE), D3 version of Grimme dispersion correction and augmented correlation-consistent polarized valence-only triple-zeta (aug-CC-pVTZ) basis set. The geometrical parameters of hydrogen bonds, binding energies, vibrational bands have been calculated and the Natural Bond Orbital (NBO), quantum theory of atoms in molecules (QTAIM) analyses have been carried out.

Adsorption of thiophene on transition metal surfaces with the inclusion of van der Waals effects

We use density functional theory with the inclusion of the van der Waals interaction to study the adsorption of thiophene, C4H4S, on Pt, Rh, Pd, Au, and Ag (100) surfaces. The five van der Waals (vdW) inclusive functionals we employ are optB86b-vdW, optB88-vdW, optPBE-vdW, revPBE-vdW, and rPW86-vdW2. For comparison we also run calculations with the GGA- Perdew Burke and Ernzerhof (PBE) functional. We examine several adsorption sites with the plane of the molecule parallel or perpendicular to the surface. The most stable configuration on all metals was the site where the center of the thiophene lies over a 4-fold hollow site with the sulfur atom lying close to a top site. Furthermore, we examine several electronic and geometric properties of the adsorbate including charge transfer, modification of the d-band, adsorption energy, tilt angle, and adsorption height. For the coinage metals PBE gives the lowest adsorption energy. For reactive transition metal substrates, revPBE-vdW and rPW86-vdW2 give lower adsorption energies than PBE.

Mechanical, Electronic, and Optical Properties of β-B6O: First-Principles Calculations

Abstract The mechanical, electronic, and optical properties of β-B6O are calculated by first-principles. The structural optimization and all properties are calculated by the method of generalized gradient approximation – Perdew, Burke and Ernzerhof (PBE). The hardness of β-B6O is 39 GPa under a pressure of 0 GPa, which indicates that it belongs to a hard material. The band gap is indirect with a value of 1.836 eV, showing that β-B6O is a semiconductor. The research of the electron localization function shows that the bonds of β-B6O are covalent bonds, which can increase the stability of the compound. The phonon dispersion curves present the dynamical stability of β-B6O under pressures of 0 and 50 GPa. The optical properties of β-B6O are also calculated. In the energy range from 0 to 18 eV, β-B6O presents high reflectivity; it has a strong absorption in the energy range from 3 to 18 eV. The refractive index results show that light propagates through the β-B6O in a difficult manner in the energy range from 6.9 to 16.5 eV. In addition, the energy of the plasma frequency for β-B6O is 16.6 eV and the peak value of the loss function is 13.6. These properties provide the basis for the development and application of β-B6O.

P 246 - Spectra of ultra-weak photon emission

Organisms undergoing oxidative metabolism or stress chemically generate electronically excited species through dioxetane and tetroxide pathways. Consequently, luminescence is emitted which could be exploited for non-invasive label-free monitoring of oxidative stress. Spectral analysis of this endogenous chemiluminescence can serve as a tool for identification of the emitters as products of oxidation. Here we employ quantum mechanical calculations and sensitive photon counting methods to obtain deeper understanding of the emitter molecules both from theoretical and experimental perspective. We focused on the analysis of carbonyl groups of simple model species (formaldehyde, acetone, etc.) and carbonyls formed by fragmentation of linoleic acid since they are common product of oxidation and also one of major emitters of endogenous chemiluminescence. We calculated emission spectra of carbonyl groups using TURBOMOLE code for quantum mechanical calculations. We used TDDFT method for excitation and emission and DFT method for optimization of the ground state. The generalized gradient approximation of Perdew, Burke and Ernzerhof (PBE) were chosen for the exchange correlation density functional. We used def2-SV(P) as basis set and the corresponding Coulomb fitting bases. We found emission spectra of individual carbonyls in water environment and in vacuum.

Structural and dynamical properties of graphite by incorporating dispersion correction: An ab-initio study

An accurate dispersion corrected study of structural and vibrational properties of graphite using the dispersion corrected density functional theory (DFT–D) is carried out. The dispersion corrected Tkatchenko and Scheffler (TS) scheme has been implemented with generalized gradient approximation (GGA) for the exchange and correlation functional in the formalism of Perdew, Burke and Ernzerhof (PBE) in order to include the long range interactions. The structural and vibrational properties of the graphite system are improved after adding the Van der Waals interactions. The calculated low frequency dispersion corrected modes of vibration have an excellent comparison with available experimental inelastic X-ray scattering and coherent inelastic neutron scattering results.

Determination of the basic physical properties of semiconductor chalcopyrite type MgSnT2 (T = P, As, Sb) from first-principles calculations

Abstract

Thermophysical Properties of LiFePO4: DFT+U Computations Combined with a Thermodynamically Self-Consistent (TSC) Method

Introduction LiFePO4 (LFP) was proposed by Padhi et al. 1 in 1997 as a promising cathode material for Li-ion batteries and very soon became the center of attention for researchers and industries in energy fields. Nowadays, it is commercialized and available in mass production through different methods. A lot of improvements in terms of material and production process have been achieved since its nascence. Nevertheless, our thermodynamic knowledge about LFP is limited to handful experimental works 2 on heat capacity and few computational studies 3 to estimate elastic properties at ground state condition. Enlarging our knowledge about thermophysical properties of LFP such as elastic properties, Debye temperature, heat capacity and also thermal expansion at higher temperatures is a crucial key to expand the thermodynamic information, and consequently to answer the arising questions about phase equilibrium in production process. Methodology Here, we present the abovementioned thermophysical properties of LFP in a wide range of temperature by Density Functional Theory (DFT) and a new Thermodynamically Self-Consistent ( TSC) method 4. The TSC method is, in summary, an extension of the quasi-harmonic approximation (QHA) satisfying the Maxwell relations and thus ensuring thermodynamic consistency. For future, we assay the effect of vacancy and also elemental substitution on thermophysical and electrochemical properties of LFP. Computational Details. We use Vienna ab initio Simulation Package (VASP) 5 to address our aim. Projected Augmented Wave (PAW) approach 6 and the General Gradient Approximation (GGA) of Perdew, Burke and Ernzerhof (PBE) 7 are used to represent the electron-ion core and electron-electron interactions, respectively. The Hubbard U correction to the GGA (GGA+U) equal to 5.3 eV for Fe in oxide systems is employed to address a correct band structure and binding energies. Our results indicate that, a cut-off energy of 520 eV and 3×4×5 Γ-centered k-points grid in first Brillouin zone with a Gaussian smearing parameter σ of 0.02 eV ensure the accuracy in energy of the system to be more than 0.01 meV. Acknowledgement. The authors would like to thank the Natural Science and Engineering Research Council of Canada (NSERC) for the financial support awarded to this project as part of the Automotive Partnership Canada (APC) program.

Half-metallicity and optoelectronic properties of V-doped zincblende ZnS and CdS alloys

In this paper, spin-polarized density functional calculations on the structural, electronic, optical and magnetic properties of the zincblende structure of the [Formula: see text] and [Formula: see text] alloys at [Formula: see text] in the ferromagnetic (FM) ordering has been investigated. The study is accomplished using the full-potential (FP) linearized augmented plane wave plus local orbital (LAPW[Formula: see text]lo) self-consistent scheme of calculations. To incorporate the exchange correlation component in the total energy calculations of the crystal, Perdew–Burke and Ernzerhof (PBE) parameterization for the generalized gradient approximation (GGA) and GGA[Formula: see text]U are employed. Basically, for both alloys, to address their structural properties, we calculated their equilibrium lattice constants, bulk moduli as well as pressure derivatives. In general, from the analysis of the obtained electronic band structure of these alloys, the half-metallic nature of [Formula: see text] and nearly half-metallic nature of the [Formula: see text] alloy are demonstrated. The plotted density of states (DOS) curves project spin-exchange splitting energy [Formula: see text] and [Formula: see text] as generated by V-3d states. It has been clearly evident that the effective potential results for the spin-down case are more striking than for the spin-up case. In order to describe the magnetic behavior of these alloys, the exchange constants [Formula: see text] (valence band) and [Formula: see text] (conduction band) as well as the magnetic moment values are estimated. The calculated results of the magnetic moment show that the main source in the reduction of the local magnetic moment of V in the alloys in comparison with its free value is a [Formula: see text]–[Formula: see text] orbital hybridization and partial transfer to nonmagnetic sites of (Zn, S) and (Cd, S) in [Formula: see text] and [Formula: see text] alloys. In addition, a study concerning optical properties, such as the refractive index, reflectivity and absorption coefficients is performed to determine their potential for optical and optoelectronic devices.

Ab initio calculations of the structure, energetics and stability of AunTi (n = 1–32) clusters

The stability and structure of titanium doped gold clusters (AunTi; n=1–32) are studied by density functional theory calculations, as implemented in the first principles code SIESTA. The exchange and correlation effects were calculated within the generalized gradient approximation (GGA) parametrized by Perdew, Burke and Ernzerhof (PBE). We used norm conserving Troullier–Martins pseudopotentials for the 10-electron valence configuration of Ti and 11-electron valence configuration of Au. All calculations were spin-polarized. The global energy minimum geometries of the clusters were searched for by using the simulated annealing technique. The stability of the clusters is discussed on the basis of the binding energy per atom, second-order energy difference, vertical ionization potential, vertical electron affinities, HOMO–LUMO energy gap and vibrational frequencies. Based on the simultaneous criteria of high binding energy, high band gap, high vertical ionization potential, and low electron affinity, it is found that Au4Ti and Au14Ti clusters have a higher stability and are candidates for “magic clusters”, which confirms the already known results from previous works. The new result presented in this paper is that the Au20Ti and Au30Ti clusters have a higher stability too. In general, the clusters with even n are more stable than the clusters with odd n. Most of the clusters with even n are non-magnetic (total magnetic moment is zero). Our results also suggest that only the Au3Ti, Au7Ti and Au8Ti clusters have a planar structure.

Role of the van der Waals interactions and impact of the exchange-correlation functional in determining the structure of glassyGeTe4

The structural properties of amorphous ${\mathrm{GeTe}}_{4}$ are studied within the framework of first-principles molecular dynamics combined with density functional theory. Four different theoretical schemes are considered, each one intended to correspond to a distinct structural model. These are obtained by selecting either the PBE (Perdew, Burke, and Ernzerhof) or the BLYP (Becke, Lee, Yang, and Parr) exchange-correlation functionals and, for each one of the two, by disregarding or including van der Waals dispersion forces. Based on the comparison with experimental total structure factor $S(k)$ and total pair correlation function $g(r)$, one can infer the quantitative character of such models, thereby extracting information on the underlying structures. We found that the inclusion of the vdW forces improves the predictive power of our approach for the PBE and (to a smaller extent) the BLYP exchange-correlation functionals. Overall, BLYP performs better than PBE in reproducing the available experimental quantities, providing a tetrahedral atomic-scale network profoundly different from the one predicted by PBE, in which tetrahedral and octahedral motifs do coexist. Our work demonstrates that a careful choice of the exchange-correlation functional, combined with the account of van der Waals forces, is crucial to achieve realistic structural predictions for glassy ${\mathrm{GeTe}}_{4}$.

First-principle investigations of structural and electronic properties of TMAl (TM = Fe, Co, and Ni) transition metal aluminides

Abstract In the present work, we have investigated the structural and electronic properties of TMAl (TM = Fe, Co, and Ni) transition metal aluminides in the B2 structure, using first-principle calculations of the density functional theory (DFT) based on the linearized augmented plane wave method (FP-LAPW) as implemented in the WIEN2k code, in which the energy of exchange and correlation are treated by the generalized gradient approximation (GGA), proposed in 1996 by Perdew, Burke and Ernzerhof (PBE). The ground state properties have been calculated and compared with other calculations, and the electronic structures of all FeAl, CoAl, and NiAl compounds exhibited a metallic behavior. It was depicted that the density of states is characterized by the large hybridization between the s-p (Al) and 3d (Fe, Co, and Ni) states, which creates the pseudogap in the region of anti-bonding states. Moreover, the band structures of FeAl, CoAl, and NiAl are similar to each other and the difference between them is in the energy level of each band relative to the Fermi level.

First principles study of scandium nitride and yttrium nitride alloy system: Prospective material for optoelectronics

Besides many other state of the art promising applications, transition metal (TM) nitride materials are intensively investigated on account of considered potential materials for optoelectronic applications. In this study computations pertaining to structural, electronic as well as the optical properties of Scandium Nitride (ScN), Yttrium Nitride (YN) and their mutual alloying (ScxY1−xN), for x=0.25, 0.50, 0.75, are presented. These computations are carried out by employing the full potential (FP) linearized augmented plane wave (LAPW) plus local orbitals (lo) method designed within density functional theory (DFT). Structural parameters are calculated at the level of Perdew Burke and Ernzerhof (PBE) parameterized generalized gradient approximations (GGA), where to investigate electronic and optical properties, Tran–Blaha modified Becke–Johnson (mBJ) potential is involved. From our calculations, a very small variation is noted in lattice constant values of ScxY1−xN alloying system as a function of Y content, reflecting to appropriate alloying of ScN and YN. Moreover, effect of the site preference for two different configurations is also analyzed. The lower absorption of ScxY1−xN system in the visible light region together with less than 30% reflectivity for entire alloying range lead to their transparent nature. Additionally fascinating characteristics, like high mechanical strength, tunable energy band gap, transparent nature, and lower reflectivity of the ScYN alloying system provoke their further potential in optoelectronics.

Multiscale Modeling of the Electrode/Electrolyte Interface Using Charge Optimized Many Body (ECOMB3) Potentials

Introduction Present day advances in computer simulation have greatly accelerated material discovery and the investigation of bulk and surface properties that are relevant to the reactivity and performance of the material. Electrocatalytic systems present unique challenges to atomistic and electronic structure modeling due to the presence of an electrode/electrolyte interface and the integration of electrical currents and chemical reactions. Our objective is to develop robust methods that can provide a reasonable atomistic description of the electrode/electrolyte interface that can be used to investigate the complex underlying interfacial chemistry. We combine Density Functional Theory (DFT) and a force field (FF) based classical approach to construct an atomistic modeling tool to consider this interface. Two key features of the electrochemical interface are incorporated - metal polarizability and the interfacial electrolyte chemistry in the presence of a potential-controlled field. In our previous study [1], we employ a reactive modified central force-field (mCF) model that uses simple point charges with pairwise interactions to model reactive water that can dissociate under the influence of potential controlled Pt (111) electrodes. The electrodes are held at constant potential by using a charge fluctuation approach called Electrode Charge Dynamics (ECD) [2]. However the mCF model assigns a fixed charge/oxidation state to the water species and the ECD scheme does not permit charge exchange between the electrode and the electrolyte. In this work, we report third-generation Charge Optimized Many Body potentials (COMB3) [3] in conjunction with an electrode charge equilibration scheme (ECOMB3) for modeling the electrified interface. This model advantageously has a on-the-fly partial charge assignment and allows for a multi-body charge equilibration within a constant potential controlled environment. Materials and Methods All molecular dynamics (MD) simulations have been carried out in Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS). The DFT calculations were conducted using the Vienna ab-initio package using a generalized gradient approximation (GGA) with the Perdew, Burke and Ernzerhof (PBE) functional. For complete simulation details and a detailed description of the COMB3 formalism, please refer to Ref. [1] and [3]. Results and Discussion An atomistic representation of the electrode/electrolyte interface is shown in Figure 1. In order to apply an electrode potential drop (ΔV) across two electrodes that are modeled as two halves of a metal slab in a periodic representation, the ECOMB3 scheme inserts a constant offset potential V, in the self-consistent charge equilibration scheme, biasing one side of the metal slab relative to the other. The atom-centered charge equilibration scheme treats transferred charge as continuous variables subject to overall charge conservation. To compute the partial charges on the individual atoms, the overall electrostatic energy (U) of the system is minimized relative to the each partial charge (qi ) (also defined as the electronegativity Χ) within the constraint that overall system is charge-balanced. When a voltage offset V is applied, the electronegativity at all sites is no longer the same and is biased at the electrodes by a magnitude of Vas shown in Equation (1). The equations of motion are then modified to accommodate the bias (Equations 2 and 3). δU cathode/δqi − δU anode/δqi = V (1) Cathode: mqqi ″ = Χ avg + (NC /NT ) V − Χi + νqi ′ (2) Anode: mqqi ″ = Χ avg − (NA /NT ) V − Χi + νqi ′ (3) where mq denotes the fictitious mass of the charge q on atom i and ν represents the velocity. NA and NC represent the number of Cu atoms at the anode and cathode respectively with the total number of atoms NT = NA + NC . The average electronegativity Χ avg of the system is computed as the sum of the electrongativity of each atom iaveraged over all atoms. We will demonstrate the use of the ECOMB3 method to study the environment in which electrocatalysis occurs. Specifically, we report the distribution and dynamics of the interfacial species, the fluctuation and distribution of charge on the electrode, and the distribution of electrostatic potential at the interface. References Yeh, K.-Y., Janik, M. J. and Maranas, J. K., Electrochimica Acta, 101, 308 (2013).Guymon, C. G., Rowley, R. L., Harb, J. N. and Wheeler, D. R., Condens. Matter Phys, 8, 335 (2005).Liang, T., Shan, T.-R., Cheng, Y.-T., Devine, B. D., Noordhoek, M., Li, Y., Lu, Z., Phillpot, S. and Sinnott, S., Materials Science and Engineering: R: Reports, 74(9), 255 (2013). Figure 1. A simulation cell of 5352 atoms consisting of Cu (111) layers acting as the cathode (Right) and anode (Left) and water (O = red, H=white) as electrolyte. Figure 1

Application of vibrational correlation formalism to internal conversion rate: case study of Cu(n) (n = 3, 6, and 9) and H2/Cu3.

This work reports non-radiative internal conversion (IC) rate constants obtained for Cun with n = 3, 6, and 9 and H2 on Cu3. The Time-Dependent Density Functional Theory (TDDFT) method was employed with three different functionals in order to investigate the electronic structures and the absorption spectra. The performance of the generalized gradient approximation of Perdew, Burke and Ernzerhof (PBE) and the hybrid B3LYP and PBE0 exchange correlation functionals in combination with the SVP and the def2-TZVP basis sets was examined. TDDFT results were used as input data to compute internal conversion rate constants. For this purpose, we have developed a program package. A description of the theoretical background used in our numerical implementation and the program input file is presented. In view of future applications of this program package in photoinduced catalysis, we present the analysis of the IC rate processes for the photodissociation of H2 on Cu3. These results showed the applicability of the method and the computational program to identify the vibrational modes in transition metal clusters giving rise to the largest IC rate constant due to their interactions with the excited electronic states occurring in the hot-electron induced dissociation phenomena.

Interaction of aluminum dimer with defective graphene

In the present work, density functional theory (DFT) calculations using cluster and slab models were performed in order to study the adsorption of Al dimer on a monovacancy of graphene. With cluster models, two different approaches were considered for the exchange and correlation functional; namely, the Perdew, Burke and Ernzerhof (PBE) and the Becke, 3-parameter, Lee–Yang–Parr (B3LYP) functionals. Under the slab approximation only PBE was employed. The geometry where two Al atoms are simultaneously adsorbed on both sides of a monovacancy (H3–H3) is the most stable thermodynamically, followed by the structure in which one Al atom resides over the center of a vacancy and the other makes a bridge between two carbon atoms (H3-B). The magnitude of the Al2 adsorption energy is larger than that of an adsorbed Al atom. While the ground states for both free Al2 and isolated defective graphene is predicted to be a triplet, that corresponding to the dimer adsorbed on the monovacancy is calculated to be a singlet. Charge population analysis has shown that a significant electron transfer from Al to the substrate of about 2e is produced. The corresponding density of states (DOS) obtained with periodic conditions indicate that the Al2/defective graphene system at the H3-B geometry with a doping level of about 3% has a nearly zero band gap with almost no states at the Fermi level, unlike the situation where only one Al atom is adsorbed on the monovacancy which present a metal-like behavior.