Binding Energy Of Atom Research Articles

On the signatures of oxygen vacancies in O1s core level shifts

Density functional theory calculations are used to investigate O1s surface core level shifts for MgO(100), ZnO(101¯0), In2O3(111) and CeO2(111). Shifts are calculated for the pristine surfaces together with surfaces containing oxygen vacancies and dissociated H2. Pristine surfaces show small negative shifts with respect to the bulk components and vacancies are found to have a minor effect on the O1s binding energies of neighboring oxygen atoms. OH-groups formed by H2 dissociation yield binding energies shifted to higher energies as compared to the oxygen atoms in the bulk. The results stress the difficulties in assigning core-level shifts and suggest that assignments of shifts in O1s binding energies to neighboring oxygen vacancies for the explored oxides should be reconsidered.

Adsorption of lead on the surfaces of pristine and B, Si and N-doped graphene

The efficacy of graphene and graphene doped with B, Si and N surfaces for the removal of Pb atom is examined by utilising density functional theory calculations. The results show that the binding energy of a single Pb atom on pristine graphene surface is −0.71 eV with the charge transfer of 0.42 electros from Pb to the surface. There is a significant enhancement observed in the binding on the surfaces of B-doped graphene (−1.46 eV) and Si-doped graphene (−2.37 eV) with the transfer of 1.48 and 1.92 electrons to their respective surfaces. The binding energy for the N-doped graphene is endothermic (+0.42 eV) due to negligible charge transfer between the Pb and the doped surface. The intense binding nature between Pb and pristine as well as the doped graphene structures is introduced, analysed and discussed in terms of bond distances, binding energies, Bader charges and electronic structures.

A Systematic Study of Structures, Stability, and Electronic Properties of Alloy Clusters Alben (N = 1–12): Comparison with Pure Beryllium Clusters

The geometric structures, energetic and electronic properties of global minima of the AlBe n ( n = 1–12) clusters have been systemically studied by using the hybrid density functional theory [B3LYP] and coupled cluster [CCSD(T)] methods. It is found that the impurity Al atom is externally bound to the host Be n framework and its maximum coordination number is six. Besides, the geometries of AlBe n bear close resemblance to either local or global minimum structures of Be n +1 . The AlBe 3 and AlBe 8 clusters exhibit high relative stability among the AlBe n clusters, which is reflected by the evolutions of average atomic binding energy, dissociation energy, second difference in energy, adsorption energy of Al, and HOMO-LUMO gap with cluster size. In comparison to the pure Be n +1 clusters, AlBe n exhibit larger binding energy values, whereas they are more polarizable.

A STUDY OF CARBON NANOTUBES ENERGETICS USING ORBITAL FREE METHOD IN THE FRAME-WORK OF THE DENSITY FUNCTIONAL THEORY

Dependence of the binding energy of carbon atoms in nanotubes on the tube diameter is studied. The full-electron orbital free modeling method, developed by us in the framework of the density functional theory, was used for calculation of the binding energy. Nanotubes of limited lengths with the armchair ends were investigated. The tube diameter D, was varied from 0,68 nm up to 1,50 nm; numbers of included atoms were changed from 80 up to 320. Three sets of tubes were studied: the tube length was 0,87 nm in the first set, 1,36 nm in second set, and 1,86 nm in the third set. For the first set the energy minimum (-7.50 eV) was found at Dmin = 1,22 nm, for the second set (-7.62 eV) at Dmin = 1.00 nm, and for the third set (-8.01 eV) at Dmin = 1.06 eV.

Stability of heterogeneous single-atom catalysts: a scaling law mapping thermodynamics to kinetics

Heterogeneous single-atom catalysts (SACs) hold the promise of combining high catalytic performance with maximum utilization of often precious metals. We extend the current thermodynamic view of SAC stability in terms of the binding energy (Ebind) of single-metal atoms on a support to a kinetic (transport) one by considering the activation barrier for metal atom diffusion. A rapid computational screening approach allows predicting diffusion barriers for metal–support pairs based on Ebind of a metal atom to the support and the cohesive energy of the bulk metal (Ec). Metal–support combinations relevant to contemporary catalysis are explored by density functional theory. Assisted by machine-learning methods, we find that the diffusion activation barrier correlates with (Ebind)2/Ec in the physical descriptor space. This diffusion scaling-law provides a simple model for screening thermodynamics to kinetics of metal adatom on a support.

First-principles investigations of hydrogen trapping in Y2O3 and the Y2O3|bcc Fe interface

Based on first-principles calculations, the binding energy of hydrogen atom to Y2O3 and Y2O3|bcc Fe interface (relative to bcc Fe side) with cube-on-cube orientation is at least 0.45 eV, if hydrogen substitutional is considered, or at least 0.26 eV if only hydrogen interstitial is considered. The calculated binding energies do not have a unique fixed value, because they are dependent on the interface structure, the Fermi level of Y2O3 near the interface and the chemical potential of Y/O. Hydrogen substitutional is more stable than hydrogen interstitial near the interface for Fermi level around calculated Schottky barrier height (SBH) at equilibrium. The Y2O3 particle interior can be an effective trapping site for hydrogen. Hydrogen interstitial, hydrogen substitutional and Y/O vacancy have a much lower energy near the interface than within the Y2O3 particle, presumably due to image charge interaction related to their non-zero charge state. For neutral impurities or defects, the energy near interface and that far away from the interface are similar (⩽0.1 eV difference) for a perfect coherent interface. The Y2O3|bcc Fe interface should provide effective trapping sites for hydrogen atoms in oxide dispersion strengthened (ODS) steels.

Thermal transport at 6H-SiC/graphene buffer layer/GaN heterogeneous interface

We investigate the epitaxial growth of graphene on SiC and thermal transport at 6H-SiC/graphene buffer layer/GaN heterogeneous interface. Under Tersoff-Erhart-Albe potential (TEA) and environment-dependent interatomic potential (EDIP), graphene buffer layer (GBL) is epitaxially grown by simulated annealing method, and simulations show that TEA potential is superior to EDIP potential by evaluation of nucleation temperature, radial distribution function, average atomic binding energy, atomic structure and bond length. Further, by thermal relaxation method, single-vacancy defects in graphene can reduce interface thermal resistance (ITR) at 6H-SiC/GBL/GaN heterogeneous interface with maximum reduction of 9.6%, meaning that ITR can be reduced by defect engineering. In addition, with the increase of nucleation areas, especially the bonding of different nucleation zones, ITR also has a highest decline of 17.9%, and energy is easier to pass through the interface, illustrating the importance of graphene integrity for interfacial heat transfer. At last, the increase in temperature (300 K to 1100 K) results in a maximum 19.6% decrease in ITR, indicating that ITR is sensitive to temperature. The selection of potential and the analysis of the heat transfer of the three-materials heterogeneous interface contribute to thermal design of graphene-based semiconductor devices.

Fly ash geopolymer mortar: Impact of the substitution of river sand by copper slag as a fine aggregate on its thermal resistance properties

Geopolymer materials are increasingly finding application in various settings because of their excellent mechanical properties and their ability to reduce the level of CO2 emission in the atmosphere, thus contributing to a sustainable environment. Mortars containing an alkali-activated fly ash binder in which river sand is used as an aggregate are found to display poor adhesive strength and incompatibility at elevated temperatures, necessitating researchers to look for alternate aggregates to be used in geopolymer mortars. In this study, we have substituted copper slag as an aggregate [C] in place of river sand [R] in a fly ash geopolymer mortar and investigated its effect on the thermal resistance of the mortar. We report the results of our investigations in this paper. Our experimental results show that the mortar using copper slag as an aggregate (C-type mortar) exhibited good thermal stability in the temperature range of 200–1000 °C without any spalling. Thermal strain was low, and the mortar was found to have a thermal expansion of just 0.002% and a thermal conductivity value of 0.6 W/m K at 1000 °C. Further, the C-type mortar exhibited a compressive strength of 33 MPa on exposure to 1000 °C and negligible mass loss even after several thermal cycles, facilitating the recycling of industrial waste such as copper slag in thermal applications. In contrast, mortars using river sand as an aggregate (R-type mortars) exhibited a higher mass loss on thermal treatment. Thermal-induced changes were studied using field emission scanning electron spectroscopy (FESEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The network rich in silicon atoms in the crystalline phase was found to contain aluminium as nepheline along with an amorphous geopolymeric gel in the heated samples. There were no differences in the binding energy of Si, Al, O and Na atoms of heated and unheated samples, which confirmed the retention of the desired geopolymeric microstructural network even at elevated temperatures.

New insights into the anti-disproportionation mechanism of ZrCo alloying with Ti, Hf, Sc, Cu, and Fe elements

First-principles calculations were performed to investigate the effects of alloying substitutions (i.e. Ti, Hf, Sc, Cu and Fe) on the anti-disproportionation ability of ZrCo alloy. For the first time, we revealed the disproportionation mechanism from the energy point of view and provided a new theoretical method to predict whether the substitution element has the ability to enhance the anti-disproportionation performance of ZrCo alloy. Based on the hydrogen atom occupancy behavior in ZrCoH3 and the results of our calculation of binding energy, the hydrogen atom migration model during hydrogenation and theoretical computational model were established. Through structural optimization, a series of stable 2 × 1 × 2 ZrCoH3 supercells were obtained, which contain four hydrogen atoms occupying 8e site and various substitution atoms with different amounts except for pure system. The binding energy of hydrogen atom in the 8e site and activation energy of diffusing from 8e site to 4c2 site of these ZrCoH3 supercells were calculated. The results showed that the substitution of Ti and Hf increased the binding energy of hydrogen atom in the 8e site, while the substitution of Fe, Cu and Sc decreased the binding energy of hydrogen atom in the 8e site. Meanwhile, both of Ti and Hf substitution reduced the activation energy of diffusing from 8e site to 4c2 site, while all of Fe, Cu and Sc substitution increased the activation energy of diffusing from 8e site to 4c2 site. These results indicated that hydrogen-induced disproportionation was the inherent property of ZrCo alloy, and element substitution can restrain or accelerate disproportionation by affecting both the binding energy and activation energy. With simultaneous consideration of the binding energy and activation energy, the effect of these alloying substitutions on the anti-disproportionation ability could be ascertained and the results were in good agreement with the previous theoretical and experimental results.

Synthesis and magnetic properties of chromium doped cobalt ferrite nanotubes

Chromium (Cr) doped cobalt ferrite (Co1−xCrxFe2O4:x = 0.0, 0.02, 0.04, 0.06, 0.08, 0.1, denoted as to CCFO) hollow nanotubes were synthesized by electrospinnig method followed by, calcining treatment at 700 °C in air. The samples exhibited a single phase cubic spinel phase. The lattice constant of the samples was found to initially decreased and thereafter increases with increased of Cr content. The morphology analysis indicated that the samples displayed a disordered arrangements of hollow structures and the relevant surfaces were rough and porous. Transmission electron microscopy (TEM) paragraph confirmed that the doped CCFO nanotubes had a polycrystalline nature and exhibited the changes in the corresponding crystal structure. X-ray photoelectron spectroscopy (XPS) confirmed that Cr doping affect the crystal structure and atomic-binding energy. The analysis of magnetic hysteresis loop indicated an obvious reduction in the saturation magnetization (Ms) of cobalt ferrite with increasing in Cr substitution. The remanent magnetization (Mr) and coercivity were increased at first and then decreased with increasing of Cr content, which was elucidated by the surface effect and magnetic moment direction. The switching field distribution analysis indicated the magnetically crystal soft phase and there were multiple-step processes to reach magnetic reversal.

An effective method to screen carbon (boron, nitrogen) based two-dimensional hydrogen storage materials

The current critical environmental pollution caused by the huge fossil fuel burning together with the increasingly scarce energy source has inspired much attention on the renewable clean hydrogen energy. Thus, the hydrogen storage materials are very vital for the hydrogen application and will be screened by the high-throughput computational screening procedure in this paper. Generally, metal-modified carbon (boron, nitrogen) nanomaterials can exhibit excellent hydrogen storage capacities. An effective procedure is designed to screen the potential metal decorated carbon (boron, nitrogen) hydrogen storage materials from the Materials Project database, which can be proved to be easily realized and reliable. Totally six ideal structures are obtained for hydrogen storage by considering the thermodynamic stability, the metal decorating, the theoretical hydrogen gravimetric density larger than 5.5 wt%, the PBE band gap smaller than 1.0 eV, and the two-dimensional structure restriction. Furthermore, the binding energy of the metal atom to the screened 2D materials, the average adsorption energy per H2 adsorbed by the metal, the density of states, the difference charge densities are calculated by the density functional method. We believe that our screening procedure can effectively and accurately search for hydrogen storage materials, which should be the theoretical basis for experimental researches.

Nitroaromatic Compounds to Induce a Partial Positive Charge on the Silver Nanoparticle Surface for Facilitated Transport Membranes for Olefin/Paraffin Separation

Two nitroaromatic compounds (NACs), 1,2-dinitrobenzene (DNB) and 3,4-dinitrotoluene (DNT), were utilized as polarizers to induce a partial positive charge on the silver nanoparticle (Ag NP) surface with the help of the strong electron withdrawing property of the nitro group. Membranes containing surface-charged Ag NPs dispersed in poly(N-vinyl pyrrolidone) showed remarkably high separation performance for propylene/propane mixtures. The mixed-gas selectivity was higher than 170, which is the highest among polymer-based membranes ever reported including composite membranes, and the propylene permeance was about 0.9 gas permeance unit (GPU). This high separation performance is due to the facilitated olefin transport, where Ag NPs with a positive charge, as an olefin carrier, interact specifically and reversibly with propylene, but not with propane. Therefore, it was found that the facilitated olefin transport yielding extremely high separation performance is strongly associated with the binding energy of silver atoms, which is a measure of the positive charge density on the Ag NP surface.

Relative stability of planar clusters B11, B12, and B13 in neutral- and charged-states

Theoretically, within the diatomic model, the relative stability of most abundant boron clusters B11, B12, and B13 with planar structures in neutral, positive and negative charged-states is studied. According to the specific (per atom) binding energy criterion, B12+ (6.49 eV) is found to be the most stable boron cluster, while B11– + B13+ (5.83 eV) neutral pair is expected to present the preferable ablation channel for boron-rich solids. Obtained results would be applicable in production of boron-clusters-based nanostructured coating materials with super-properties such as lightness, hardness, conductivity, chemical inertness, neutron-absorption, etc., making them especially effective for protection against cracking, wear, corrosion, neutron- and electromagnetic-radiations, etc.

A Systematic Search for the Geometric Structures, Stabilities and Electronic Properties of Bimetallic CsAu(0,±1)n Clusters

The geometric structures, relative stabilities, growth-pattern behaviors, and electronic properties of neutral and charged CsAun(0,±1) clusters have been systematically investigated with the general gradient approximation (GGA) exchange correlation density functional theory (TPSSTPSS) and a relativistic effective core potential, together with a vibrational frequency anslysis. The optimized geometric structures show that the ground-state structures have three-dimensional (3D) structures from n = 4 and that the doped Cs atoms tend to locate at the symmetry and surface position. One gold-atom-capped CsAun−1(0,±1) structure for CsAun(0,±1) clusters with increasing number of Au atoms is the dominant growth pattern. The total energies and the averaged atomic binding energies exhibit a sequence of CsAun− > CsAun > CsAun+ , which indicates that the stability of anionic CsAun− clusters is higher than that of neutral CsAun clusters and that the CsAun clusters is more stable than the cationic CsAun+ clusters. The relative stabilities are examined based on the analysis of the averaged atomic binding energy and the second-order difference energy, and the results indicate that the CsAu3, CsAu6+ and CsAu2− clusters are the most stable clusters. Based on the analysis of the frontier molecular orbitals, we find that the CsAun(0,±1) (n = 1 − 10) clusters can more easily acquire electrons and that the loss of electrons is difficult. The highest occupied-lowest unoccupied molecular orbital (HOMO-LUMO) gaps exhibit significant even-odd oscillation behavior. The higher gaps are exhibited by neutral CsAun clusters with odd numbers of gold atoms and ionic CsAun±1 clusters with even numbers of gold atoms. Especially, the CsAu3, CsAu6+ and CsAu6− clusters have the highest HOMO-LUMO gaps, which proves again that CsAu3, CsAu6+ and CsAu2− clusters are the most stable and the magic structures. Because of the electronegativity of Au is higher than that of the Cs atom, the charge transfers from the Cs atoms to the Aun frames in the CsAun+1 clusters. Furthermore, we have calculated the dissociation energies and found that the CsAun+ clusters have lower dissociation energies. This indicates that CsAun+ clusters are easy to dissociate and less stable. The dissociation energies of the CsAun and the CsAun− clusters exhibit a generally opposite odd-even behavior.

Using Photoionization Efficiency Spectroscopy and Density Functional Theory to Investigate Charge Transfer Interactions in AuCe3On Clusters.

The characteristics of small cerium oxide and gold-cerium oxide clusters were investigated as models for gold attachment to various defect sites on a ceria surface. Photoionization efficiency (PIE) spectra of gas phase Ce3On (n = 0-4) and AuCe3On (n = 0-3) clusters were recorded and compared to spectral simulations based on DFT calculations. Calculated structures and PIE spectra for the Ce3O5,6 and AuCe3O4-6 clusters are also presented; however, these species were not detected during photoionization experiments. Addition of an Au atom to Ce3 was found to increase the energy of the ionization onset by ∼0.4 eV, whereas addition of one or more oxygen atoms decreases the onset by ∼0.25 eV. The optimized AuCe3On (n = 0-4) cluster geometries correlate with Au atoms adsorbed to oxygen vacancy sites while the AuCe3O5 and AuCe3O6 clusters are consistent with Au adsorption to CeO3 and CeO2 vacancies, respectively. The interactions between the cerium oxide cluster surface and the adsorbed Au atom were found to strongly depend on the nature the of the adsorption site. Au adsorbed to O vacancies are negatively charged with a Ce → Au charge transfer, whereas Au adsorbed to CeO2 and CeO3 vacancies have a reversed Au → Ce charge transfer, resulting in a positively charged Au atom. Au adsorption to the Ce3On clusters has the effect of (i) reducing the differences in the HOMO energies of the AuCe3O4, AuCe3O5, and AuCe3O6 clusters and (ii) lowering the binding energy of oxygen atoms for all AuCe3On (n = 1-6) clusters. Au adsorption appears to have a minimal effect on CeO2 vacancy formation, although CeO2 vacancies were calculated to form more readily than O vacancies on both the Ce3On and AuCe3On clusters. The low energy fragmentation calculated for the Ce3O5,6 and AuCe3O4-6 clusters, via loss of either Au, O, or CeO2, could potentially make photoionization experiments unfeasible since these clusters may simply dissociate when exposed to high energy photons above the ionization threshold.

New insights into the mechanism of yttrium changing high-temperature oxide growth of Fe-13Cr–6Al–2Mo–0.5Nb alloy for fuel cladding

The oxidation behavior and microstructure evolution of Fe–13Cr–6Al–2Mo–0.5Nb alloys with various yttrium contents ranging from 0 to 0.23 wt.% have been investigated at 1200 °C for 4 h in steam environment. The oxide weight gain decreased with minor addition of yttrium, but this tendency was lost with excess addition. The grain boundary migration was hindered due to high binding energy of yttrium atom and vacancy. The combination of yttrium with vacancies and a large number of fine Laves phases at grain boundaries suppressed the outward diffusion of Al3+, resulting in the change of oxide growth mechanism and oxide scale adhesion.

QED theory of the normal mass shift in few-electron atoms

The electron-electron interaction correction of first order in $1/Z$ to the one-electron part of the nuclear recoil effect on binding energies in atoms and ions is considered within the framework of the rigorous QED approach. The calculations to all orders in $\alpha Z$ are performed for the $1s^2$ state in heliumlike ions and the $1s^2 2s$ and $1s^2 2p_{1/2}$ states in lithiumlike ions in the range $Z=5$--$100$. The results obtained are compared with the Breit-approximation values. The performed calculations complete a systematic treatment of the QED nuclear recoil effect up to the first order in $1/Z$. The correction obtained is combined with the previously studied two-electron part as well as the higher-order electron-correlation corrections evaluated within the Breit approximation to get the total theoretical predictions for the mass shifts.

Improving the adsorption potential of chitosan for heavy metal ions using aromatic ring-rich derivatives

This study describes the simple preparation process of modified chitosan (CS) that can effectively adsorb lead ion in the aqueous medium. To design this adsorbent with high binding sites, the Schiff base ligand with three aromatic rings, 3,3-diphenylpropylimine methyl benzaldehyde (PPIMB), is synthesized. The PPIMB forms several new binding sites in modified CS by making a new imine bond with free NH2 in CS structure. The structural and physicochemical characteristics of the magnetically modified chitosan (MCS-PPIMB) are evaluated by FTIR, XRD, SEM, EDX, DLS, VSM, and TG techniques. The effect of some factors, such as pH, collision time, adsorbent dosage, and initial concentration of Pb(II), is investigated on the adsorption capacity of the adsorbent. The adsorption capacity of MCS-PPIMB against Pb(II) is obtained 230.48 mg/g. The adsorption behavior of MCS-PPIMB is fitted efficiently by the Langmuir isotherm model. The fluorometric studies show that the adsorbent has a sharp emission peak at 698 nm, and Pb(II) ion can quench the fluorescence emission of MCS-PPIMB at low concentration. The theoretical studies confirm the strong binding energy of the Pb atom with aromatic rings and imine groups of the MCS-PPIMB.

Study of the ionization efficiency for nuclear recoils in pure crystals

We study the basic integral equation in Lindhard's theory describing the energy given to atomic motion by nuclear recoils in a pure material when the atomic binding energy is taken into account. The numerical solution, which depends only on the slope of the velocity-proportional electronic stopping power and the binding energy, leads to an estimation of the ionization efficiency which is in good agreement with the available experimental measurements for Si and Ge. In this model, the quenching factor for nuclear recoils features a cut-off at an energy equal to twice the assumed binding energy. We argue that the model is a reasonable approximation for Ge even for energies close to the cutoff, while for Si is valid up to recoil energies greater than ~500 eV.

Adsorption and dissociation of CO on metal clusters

Adsorption and dissociation of carbon monoxide on metal clusters M13 (M = Ag, Co, Cu, Fe, Ni and Ru), has been studied. Structure stabilities of metal clusters, adsorption sites, adsorption energies and the activation energies for the dissociation of CO were determined using density functional theory. Cohesive and binding energies of metal atoms in M13 clusters of studied metals were calculated, showing the different strength interaction of metal atoms in each particle. Three active adsorption sites on the M13 particles studied have been identified, showing that CO adsorption with covalent nature can occur on different sites depending of the metal cluster. Charge density difference in the M13-CO interaction on all the adsorption sites of all metal clusters showed a strong accumulation of charge density in the MC bonding. Of the group of metal cluster modeled, Ru13, Cu13 and Co13 present higher adsorption energies. On the other hand, Fe13, Co13 and Ru13 present lower activation energies. In all cases, endothermic behavior of CO dissociation was observed. The initial stages of CO interaction with several metal clusters, in comparison with metal surfaces, is presented.