Papers by Keyword: Electronic Property

Abstract: The widely investigated perovskite oxides has attracted for a long time a great interest on the physical properties, in their bulk structures as well as the heterostructures components. The Lanthanum transition metal oxides LaMO₃ (M= Transition metal) is part of, due to their potential use in advanced technology (including superconductivity, magnetoresistance, ionic conductivity, and a multitude of dielectric properties). Despite the broad exploration of the physical properties, we found a considerable lack in the investigation of the mechanical properties of the LaMO₃ compounds. By applying the Density Functional Theory (DFT), we shed light on the structural, electronic, and especially mechanical properties of the experimentally verified phases of The LaMnO₃, and LaNiO₃. We first calculated the structural and electronic properties, then we continue with the single-crystal elastic constants and mechanical properties, where the bulk, shear and Young’s moduli, and the Anisotropy indexes were deduced, in order to remedy the existing gap of the theoretical knowledge about the mechanical behavior of the LaMnO₃, and LaNiO₃ compounds.

Abstract: Using a first-principles methodology we have investigated the interfacial and bonding characteristics of the Al(001)/Fe (0-11) interface. The Al/Fe interface model was developed using a face-to-face matching method. Among many possible interface structures, the Al (001)/ Fe(0-11) orientation relation gave the minimum lattice misfit along the a and b directions (a=b= -0.47%). Hence, this interface structure provided the minimum energy value and was used for this study. To predict the interface strength and stability, the work of separation and interfacial energy were calculated. Here, all systems were calculated under exactly the same conditions (k-point mesh, cutoff energy, lateral lattice strain etc). In order to predict the bonding nature at the interface, charge density difference plot was evaluated, which showed charge gain at the interface. The aim of this study is to describe the adhesive behavior between Al and Fe, provide some insights about strength and stability of this interface structure for galling, and provide reference interface system for Al/Fe welding.

Abstract: We investigate the electronic, dynamic and thermodynamic properties of α-MnO₂ using first-principles calculations based on density functional theory (DFT) with the GGA+U method. The results of electronic structures show that α-MnO₂ is a semiconductor with a direct band gap of 1.4 eV at Γ point. The results of dynamic properties indicate that the structure of α-MnO₂ is dynamically unstable at ground-state. Several important thermodynamic quantities, such as entropy, enthalpy and Gibbs free energy, et al each as a function of temperature were presented.

Abstract: Ab initio electronic structures for β-Ge₃N₄ are investigated using ultrasoft pseudo-potential method within the generalized gradient approximation functional. The lattice parameters are predicted theoretically, and are compared with available experimental data and the other theoretical results. The elastic constants calculations reveal that the phenacite structure is a stable phase in the pressure range of 020GPa. The high bulk modulus (B=180.2GPa) indicates that β-Ge₃N₄ is a relatively hard material. β-Ge₃N₄ has a direct band gap of 2.94eV, indicating its promising applications as a semiconductor in electronics and optical fibers. On the other hand, the density of states analysis is also included in this paper.* Corresponding author: CHEN Dong

Abstract: Calculations have been performed for the structures and electronic properties of GaN nanoribbons with armchair edge (AGaNNRs), using the first-principles projector-augmented wave (PAW) potential within density functional theory (DFT) framework. The lowest unoccupied conduction band (LUCB) and the highest occupied valence band (HOVB) are always separated, representing a semiconductor character for the AGaNNRs. In addition, the majority and minority spin bands are fully superposition and therefore the AGaNNRs are non-magnetic. As the nanoribbons width increase, band gaps of AGaNNRs decrease monotonically and become close to their asymptotic limit of a single layer of GaN sheet.

Abstract: We have performed the first-principles calculations onto the structural and electronic properties of GaN nanoribbons with zigzag edge (ZGaNNRs). The results show that, the lowest unoccupied conduction band (LUCB) and the highest occupied valence band (HOVB) are always separated, representing a semiconductor character for the ZGaNNRs. In addition, the majority and minority spin bands are fully superposition and therefore the ZGaNNRs are non-magnetic. As the nanoribbons width increase, band gaps of ZGaNNRs decrease monotonically and become close to their asymptotic limit of a single layer of GaN sheet. It is found that the fewer coordination number will lead the most electrons to range in higher energy region of the occupancy state.

Abstract: The electronic and reaction properties of natural sphalerite containing seven typical kinds of impurities is studied by the density-functional theory (DFT). Mn and Ga impurities result in the Mulliken charge of the Zn atom reduced and consequently might decrease the ionicity of sphalerite; while Fe, Cd, In, Ge and Tl impurities lead to the increase in the Mulliken charge of the Zn atom. The frontier orbital calculations show that Mn impurities might lead to the over-oxidization of sphalerite, which may cause the further oxidation of lead xanthate, and thus are unfavorable for the flotation of sphalerite.

Abstract: Structure stability and electronic properties of Fe-doped boron carbides (B₁₃C₂) were studied using the first principle calculations based on plane wave pseudo-potential theory. The calculated results showed that the Fe-doped boron carbide representative stable structural is Fe substituting C atom on the end of chain C-B-C. The band structure and density of states (DOS) indicated that the coexistence of [C-B-Fe] ε+-[B11C] ε- structural unit made electrical conductivity increased. As the covalent bond of Fe-B was weaker than those of B-B and B-C, the thermal conductivity decreased for Fe-doped B13C2, thermoelectric property of Fe-doped boron carbides has been improved.

Abstract: Structure, electronic property, aromaticity and vibrational frequency of medium-sized Au-doped germanium clusters were systematically explored using the density-functional theory (DFT) in conjunction with the LanL2DZ basis set. Our results show that the endohedrally Au-doped cagelike structures are energetically preferred. The p- and d-states in endohedral Au atom mainly contribute to the chemical bonding at around −6.5 and −10.6 eV for the AuGe10 and AuGe12 clusters. Moreover, the cage aromaticity appears to be an important determination of the electronic stability of the two clusters, reflected by negative nucleus-independent chemical shifts (NICS) values. The theoretical work will be useful and helpful for the understanding in the further application, i.e., cluster-assembled optoelectronic nanomaterials.

Abstract: The equilibrium structures of orthorhombic LaCrO₃ (O-LaCrO₃) and rhombohedral LaCrO₃ (R-LaCrO₃) crystals were investigated by using the plane-wave self consistent field (PWSCF) method based on density functional theory (DFT). The optimized lattice parameters for both phases are in accordance with experimental results reported in literature, confirming the reliability of LSDA+U scheme used in the calculations. We have quantificationally investigated the binding energies and electronic properties of these two types of LaCrO₃ crystals. The negative total energy and binding energies indicate the ground state property and the good structrual stability of O-LaCrO₃ crystal, which is important for the preparation of nano materials, the synthesis of ceramic materials made of doped O-LaCrO₃ crytals, as well as their applications in high technology fields, and predict the metastable property of R-LaCrO₃ crystal. Furthermore, the band structures show that O-LaCrO₃ is a direct semiconductor with wide energy gap, while R-LaCrO₃ is an indirect semiconductor with narrow energy gap. The interaction between Cr and O atoms in O-LaCrO₃ crystal possesses the character of covalent bonding.