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First-principles calculations are used to systematically investigate the geometric and electronic structures of both pure TMn (n=2–4) and Ag-modulated AgTMn-1 (n=2–4; 3d-transition metal (TM): from Sc to Cu; 4d-TM: from Y to Ag elements) clusters. Some new ground state structures are found for the pure TMn clusters, such as a low symmetry configuration for Cr3, which is found to be about 0.20 eV more stable than the previously reported C2v symmetry. In the most cases, Ag-doping can significantly elongate the bond lengths of the clusters and induce geometric distortions of the small clusters from the high dimensional to the low dimensional configurations. Importantly, introduction of Ag significantly changes the electronic structures of the small clusters and modulates the density of states in the proximity of the Fermi levels, which also varies with the size and the type of the cluster. The results contribute to future design of effective bimetallic alloy Ag/TM catalysts. [ABSTRACT FROM AUTHOR]

Using gradient-corrected density functional theory and supercell technique, we have calculated total energies, electronic structure, and magnetic properties of Cr-doped ZnTe in both bulk and thin-film configurations. Calculations with full geometry optimization for a Zn1-xCrxTe supercell were carried out for different Cr concentrations (x=0.095, 0.143, and 0.19) and by varying the sites Cr atoms occupy. We show that the ferromagnetic phase of Zn1-xCrxTe in both bulk and thin film is energetically the most preferable state irrespective of the concentration and/or site occupation of the Cr atom. The strong hybridization between Cr 3d and Te 5p states is found to be responsible for the ferromagnetic coupling, in agreement with recent experiments. [ABSTRACT FROM AUTHOR]

We combined first-principles calculations with optical spectroscopy and variable-temperature film growth techniques to comprehensively investigate the electronic structure of NiFe2O4. We find this system to be an indirect-gap material in the minority channel, with two higher-energy direct-gap structures in the minority and majority channels, respectively. An analysis of states near the band edge simultaneously exposes both the charge transfer and Mott limits of the Zaanen-Sawatzky-Allen classification scheme. The gap hierarchy is well suited for spintronics applications. [ABSTRACT FROM AUTHOR]

First-principles studies are performed on Au12W@Si60 by using projector-augmented wave (PAW) method and generalized gradient approximation for the exchange-correlation energy. The geometry, electronic structure, orbital hybridization, and charge transfer are discussed. It is found that the magic Au12W cluster interacts strongly with Si, thus stabilizes Si60 cage structure. Meanwhile the metal cluster is dissociated when encapsulated in the Si60 cage, and charges are transferred from the Si cage to the metal atoms. [ABSTRACT FROM AUTHOR]

Using photoelectron spectroscopy and first principles molecular orbital calculations, we report the first observation of an abrupt change in the electronic structure of W4Om− (m⩽6) clusters at m=5 which is well below the bulk stoichiometric composition of tungsten oxide (WO3). The signature of this onset is established from an anomalous increase in the vertical detachment energies (VDE), adiabatic electron affinities (AEA), and the energy gaps between highest occupied (HOMO) and lowest unoccupied molecular orbitals (LUMO). These changes are also accompanied by the cleavage of 50% of the W–W bonds and localization of electron charge density in W4O5 cluster. [Copyright &y& Elsevier]

Stability, reconstruction, and electronic structure of a bilayer graphone have been studied, where the most stable configuration undergoes a (1×2) surface reconstruction. An energy barrier of 1.83 eV separates this structure from the nonbonded state. The stability of the reconstructed bilayer at room temperature is confirmed by both frequency calculation and molecular dynamics simulation. Unlike the graphone sheet, the bilayer graphone is nonmagnetic but remains metallic due to the existence of delocalized π orbital on the zigzag sp2 carbon chains, which are stable against Peierls instability. The metallicity is also stable under gate external electric field. [ABSTRACT FROM AUTHOR]

Abstract: Using first principles theory based on density functional formulation we have studied the interactions of uranium atom with tetraketone complexes used for all-uranium redox flow battery. The geometry and electronic structures are studied in detail. We found that uranium atom interacts strongly with tetraketone complexes, the interaction energy is more than 7.0eV, and uranium atom acts as an electron acceptor with about 0.6 electrons transferred from tetraketone complexes, while uranium atom carries the magnetic moment of 2 μ B. [Copyright &y& Elsevier]

Abstract: The geometry, electronic structure, and reactivity with O2 molecules of an isolated W@Si12 cluster have been investigated by first principles simulations. The results confirm that O2 can weakly adsorb on the HP-W@Si12 cage with a binding energy of 0.004 to 0.027 eV. O2 may dissociate on the cluster by overcoming energy barrier of at least 0.593 eV. However, this is a spin-forbidden reaction, rendering the high inertness of the HP-W@Si12 cluster toward O2. These results confirm the high inertness of the W@Si12 cluster toward O2 molecules in ambient conditions, in close agreement with experimental observations of magic cluster of W@Si12. [Copyright &y& Elsevier]

First-principles calculations within the density-functional theory (DFT) have been carried out to study the geometric and electronic structures of Pbn clusters with dimensions of up to 3 nm. As distinguished from prolate silicon, germanium, and tin clusters, amorphouslike lead clusters containing more independent pentagonal bipyramid Pb7 units are more favorable than octahedral (Oh) fragments as n up to 147. On the other hand, covalently bonded Pb7 units obstruct the electronic delocalization process, i.e., the transition from clusters to metallic bulk characters. The average bond length (charge density) within the Pb7 unit is usually shorter (higher) than that among the Pb7 units. By tracing two kinds of bond forms in the Pb7 unit and between Pb7 units, we find that the melting process begins from the weaker bond between the Pb7 units. The existence of significant covalent bonding in metal clusters may also generally hold for explaining why some Sn and Pb clusters also remain solid above the bulk melting temperature as previously reported. [ABSTRACT FROM AUTHOR]

Abstract: First-principles calculations have been applied to investigate the role of Ni-doping in modifying the geometric and electronic structures of Cu n clusters (), and the chemical activity of clusters towards CO2. The results reveal that Ni-doping introduces a significant modulation of the electronic structures, such as the density of states, HOMO–LUMO gaps and the d-band centers, which dominate their chemical activities towards CO2 adsorption. Our findings contribute valuable information for high efficient Cu–Ni alloy nano-catalyst design. [Copyright &y& Elsevier]

Abstract: The effect of different vacancies on the morphology of the O-terminated Cu2O(111) surface has been studied through the first-principles calculations. Our results show that Cu and O vacancies trigger large relaxations and formation of two different facets. Our emulated STM images are in consistent with the experimental STM patterns. A sizeable magnetic moment (∼1.0 μB) was found for surfaces with either Cu or O vacancies. The calculated formation energies of surface vacancies indicate that the deficient surfaces are more stable than the stoichiometric O-terminated surface, which is also in line with our results obtained from ab initio atomistic thermodynamics studies. [Copyright &y& Elsevier]