The Experts below are selected from a list of 81 Experts worldwide ranked by ideXlab platform
Ruizhou Zhang - One of the best experts on this subject based on the ideXlab platform.
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First-principles study of the electronic and optical properties of a new metallic MoAlB
Scientific Reports, 2016Co-Authors: Xiaohong Li, Ruizhou ZhangAbstract:The structural, elastic, electronic and optical properties of MoAlB were investigated by first-principles calculations. The hardness of MoAlB is 12.71 GPa, which is relatively softer and easily machinable compared to the other borides. The analysis of the band structure and density (DOS) of states indicates that MoAlB has a metallic nature. The analysis of the electron localization function (ELF) shows that the Mo-B Bond is a Polar Covalent Bond with a short distance, which may increase the stability of the compound. The calculation of the phonon frequencies confirms the dynamical stability of MoAlB. Optical properties of MoAlB are investigated. In the energy range up to ~19 eV, MoAlB possesses high reflectivity and has the strongest absorption in the energy range of 0–23.0 eV. In addition, the plasma frequency of MoAlB is 20.4 eV and MoAlB can change from a metallic to a dielectric response if the incident light has a frequency greater than 20.4 eV.
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First-principles study of the electronic and optical properties of a new metallic MoAlB
Scientific Reports, 2016Co-Authors: Xiaohong Li, Hongling Cui, Ruizhou ZhangAbstract:The structural, elastic, electronic and optical properties of MoAlB were investigated by first-principles calculations. The hardness of MoAlB is 12.71 GPa, which is relatively softer and easily machinable compared to the other borides. The analysis of the band structure and density (DOS) of states indicates that MoAlB has a metallic nature. The analysis of the electron localization function (ELF) shows that the MoB Bond is a Polar Covalent Bond with a short distance, which may increase the stability of the compound. The calculation of the phonon frequencies confirms the dynamical stability of MoAlB. Optical properties of MoAlB are investigated. In the energy range up to ~19 eV, MoAlB possesses high reflectivity and has the strongest absorption in the energy range of 0-23.0 eV. In addition, the plasma frequency of MoAlB is 20.4 eV and MoAlB can change from a metallic to a dielectric response if the incident light has a frequency greater than 20.4 eV. "MAX-phase" is a family of layered transitional metal carbides and nitrides with general formula M n+1 AX n with n = 1-3, where M is an early transition metal, A is a group IIIA-IVA element, and X is either carbon or nitrogen 1. Most of these phases were discovered in the 1960 s. Since the 1960 s, research on these phases has increased dramatically, and 413 subgroup and several new MAX phases were discovered 2,3. Research shows that the MAX-phases possess attractive properties, combining the merits of metals and ceramics such as high melting temperature, high elastic stiffness, good machinability, and high thermal and electrical conductivity 4-6. These important metallic and ceramic properties of the MAX phases are determined by their structures, which consist of stacked layers of M-X octahedra separated by mono-atomic A "metallic" layers 7. Mo-base MAX phases have many attractive properties and have established the research field in recent years. In 1942, Halla and Thury first described MoAlB 8 , then in 1966, Jeitschko et al. 9 discovered the MoAlB (space Cmcm) ternary transition metal boride and found that its structure was similar to the MAX phases. In 1995, Yu and Lundstrom 10 presented crystal growth and structure refinement of Mo 1−x Cr x AlB (x = 0,31). Rieger et al. 11 discovered that MoAlB has relatively lower hardness than WAlB and higher electrical conductivity than WAlB. Compared with Ti 2 AlC and Cr 2 AlC 12,13 , the Al content in MoAlB would form upon heating in air. The all-electron projector augmented wave (PAW) method is an efficient method to be used in ab initio electronic structure calculations of periodic systems. Zhang et al. 14 predicted the structure of ZrB 4 and investigated the mechanical, and electronic properties of ZrB 4 by using the PAW method. Wang et al. 15 used the PAW method to investigate the novel superhard B-CO phases and thought that B 4 CO 4 is potentially superhard. Tang et al. 16 investigated the phonon dispersion and elastic constants of orthorhombic CN and thought that CN is a potential superhard material, using the PAW method. In this article, the equilibrium atomic structures of MoAlB are calculated and compared with the available experimental values by using the PAW method. Optical properties such as the dielectric function and the refrac-tivity and electronic properties such as the density of states (DOS), the electron localization function (ELF) and the band structure were further investigated. We consider our work to be a starting point for further theoretical and experimental work for MoAlB.
Xiaohong Li - One of the best experts on this subject based on the ideXlab platform.
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First-principles study of the electronic and optical properties of a new metallic MoAlB
Scientific Reports, 2016Co-Authors: Xiaohong Li, Ruizhou ZhangAbstract:The structural, elastic, electronic and optical properties of MoAlB were investigated by first-principles calculations. The hardness of MoAlB is 12.71 GPa, which is relatively softer and easily machinable compared to the other borides. The analysis of the band structure and density (DOS) of states indicates that MoAlB has a metallic nature. The analysis of the electron localization function (ELF) shows that the Mo-B Bond is a Polar Covalent Bond with a short distance, which may increase the stability of the compound. The calculation of the phonon frequencies confirms the dynamical stability of MoAlB. Optical properties of MoAlB are investigated. In the energy range up to ~19 eV, MoAlB possesses high reflectivity and has the strongest absorption in the energy range of 0–23.0 eV. In addition, the plasma frequency of MoAlB is 20.4 eV and MoAlB can change from a metallic to a dielectric response if the incident light has a frequency greater than 20.4 eV.
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First-principles study of the electronic and optical properties of a new metallic MoAlB
Scientific Reports, 2016Co-Authors: Xiaohong Li, Hongling Cui, Ruizhou ZhangAbstract:The structural, elastic, electronic and optical properties of MoAlB were investigated by first-principles calculations. The hardness of MoAlB is 12.71 GPa, which is relatively softer and easily machinable compared to the other borides. The analysis of the band structure and density (DOS) of states indicates that MoAlB has a metallic nature. The analysis of the electron localization function (ELF) shows that the MoB Bond is a Polar Covalent Bond with a short distance, which may increase the stability of the compound. The calculation of the phonon frequencies confirms the dynamical stability of MoAlB. Optical properties of MoAlB are investigated. In the energy range up to ~19 eV, MoAlB possesses high reflectivity and has the strongest absorption in the energy range of 0-23.0 eV. In addition, the plasma frequency of MoAlB is 20.4 eV and MoAlB can change from a metallic to a dielectric response if the incident light has a frequency greater than 20.4 eV. "MAX-phase" is a family of layered transitional metal carbides and nitrides with general formula M n+1 AX n with n = 1-3, where M is an early transition metal, A is a group IIIA-IVA element, and X is either carbon or nitrogen 1. Most of these phases were discovered in the 1960 s. Since the 1960 s, research on these phases has increased dramatically, and 413 subgroup and several new MAX phases were discovered 2,3. Research shows that the MAX-phases possess attractive properties, combining the merits of metals and ceramics such as high melting temperature, high elastic stiffness, good machinability, and high thermal and electrical conductivity 4-6. These important metallic and ceramic properties of the MAX phases are determined by their structures, which consist of stacked layers of M-X octahedra separated by mono-atomic A "metallic" layers 7. Mo-base MAX phases have many attractive properties and have established the research field in recent years. In 1942, Halla and Thury first described MoAlB 8 , then in 1966, Jeitschko et al. 9 discovered the MoAlB (space Cmcm) ternary transition metal boride and found that its structure was similar to the MAX phases. In 1995, Yu and Lundstrom 10 presented crystal growth and structure refinement of Mo 1−x Cr x AlB (x = 0,31). Rieger et al. 11 discovered that MoAlB has relatively lower hardness than WAlB and higher electrical conductivity than WAlB. Compared with Ti 2 AlC and Cr 2 AlC 12,13 , the Al content in MoAlB would form upon heating in air. The all-electron projector augmented wave (PAW) method is an efficient method to be used in ab initio electronic structure calculations of periodic systems. Zhang et al. 14 predicted the structure of ZrB 4 and investigated the mechanical, and electronic properties of ZrB 4 by using the PAW method. Wang et al. 15 used the PAW method to investigate the novel superhard B-CO phases and thought that B 4 CO 4 is potentially superhard. Tang et al. 16 investigated the phonon dispersion and elastic constants of orthorhombic CN and thought that CN is a potential superhard material, using the PAW method. In this article, the equilibrium atomic structures of MoAlB are calculated and compared with the available experimental values by using the PAW method. Optical properties such as the dielectric function and the refrac-tivity and electronic properties such as the density of states (DOS), the electron localization function (ELF) and the band structure were further investigated. We consider our work to be a starting point for further theoretical and experimental work for MoAlB.
Hongling Cui - One of the best experts on this subject based on the ideXlab platform.
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First-principles study of the electronic and optical properties of a new metallic MoAlB
Scientific Reports, 2016Co-Authors: Xiaohong Li, Hongling Cui, Ruizhou ZhangAbstract:The structural, elastic, electronic and optical properties of MoAlB were investigated by first-principles calculations. The hardness of MoAlB is 12.71 GPa, which is relatively softer and easily machinable compared to the other borides. The analysis of the band structure and density (DOS) of states indicates that MoAlB has a metallic nature. The analysis of the electron localization function (ELF) shows that the MoB Bond is a Polar Covalent Bond with a short distance, which may increase the stability of the compound. The calculation of the phonon frequencies confirms the dynamical stability of MoAlB. Optical properties of MoAlB are investigated. In the energy range up to ~19 eV, MoAlB possesses high reflectivity and has the strongest absorption in the energy range of 0-23.0 eV. In addition, the plasma frequency of MoAlB is 20.4 eV and MoAlB can change from a metallic to a dielectric response if the incident light has a frequency greater than 20.4 eV. "MAX-phase" is a family of layered transitional metal carbides and nitrides with general formula M n+1 AX n with n = 1-3, where M is an early transition metal, A is a group IIIA-IVA element, and X is either carbon or nitrogen 1. Most of these phases were discovered in the 1960 s. Since the 1960 s, research on these phases has increased dramatically, and 413 subgroup and several new MAX phases were discovered 2,3. Research shows that the MAX-phases possess attractive properties, combining the merits of metals and ceramics such as high melting temperature, high elastic stiffness, good machinability, and high thermal and electrical conductivity 4-6. These important metallic and ceramic properties of the MAX phases are determined by their structures, which consist of stacked layers of M-X octahedra separated by mono-atomic A "metallic" layers 7. Mo-base MAX phases have many attractive properties and have established the research field in recent years. In 1942, Halla and Thury first described MoAlB 8 , then in 1966, Jeitschko et al. 9 discovered the MoAlB (space Cmcm) ternary transition metal boride and found that its structure was similar to the MAX phases. In 1995, Yu and Lundstrom 10 presented crystal growth and structure refinement of Mo 1−x Cr x AlB (x = 0,31). Rieger et al. 11 discovered that MoAlB has relatively lower hardness than WAlB and higher electrical conductivity than WAlB. Compared with Ti 2 AlC and Cr 2 AlC 12,13 , the Al content in MoAlB would form upon heating in air. The all-electron projector augmented wave (PAW) method is an efficient method to be used in ab initio electronic structure calculations of periodic systems. Zhang et al. 14 predicted the structure of ZrB 4 and investigated the mechanical, and electronic properties of ZrB 4 by using the PAW method. Wang et al. 15 used the PAW method to investigate the novel superhard B-CO phases and thought that B 4 CO 4 is potentially superhard. Tang et al. 16 investigated the phonon dispersion and elastic constants of orthorhombic CN and thought that CN is a potential superhard material, using the PAW method. In this article, the equilibrium atomic structures of MoAlB are calculated and compared with the available experimental values by using the PAW method. Optical properties such as the dielectric function and the refrac-tivity and electronic properties such as the density of states (DOS), the electron localization function (ELF) and the band structure were further investigated. We consider our work to be a starting point for further theoretical and experimental work for MoAlB.
Daniel Sánchez-portal - One of the best experts on this subject based on the ideXlab platform.
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First-Principles Study of the Electronic and Magnetic Properties of Defects in Carbon Nanostructures
Topological Modelling of Nanostructures and Extended Systems, 2013Co-Authors: Elton J. G. Santos, Andrés Ayuela, Daniel Sánchez-portalAbstract:Understanding the magnetic properties of graphenic nanostructures is instrumental in future spintronics applications. These magnetic properties are known to depend crucially on the presence of defects. Here we review our recent theoretical studies using density functional calculations on two types of defects in carbon nanostructures: substitutional doping with transition metals, and sp3-type defects created by Covalent functionalization with organic and inorganic molecules. We focus on such defects because they can be used to create and control magnetism in graphene-based materials. Our main results are summarized as follows: 1. Substitutional metal impurities are fully understood using a model based on the hybridization between the d states of the metal atom and the defect levels associated with an unreconstructed D3h carbon vacancy. We identify three different regimes, associated with the occupation of distinct hybridization levels, which determine the magnetic properties obtained with this type of doping. 2. A spin moment of 1.0 μ B is always induced by chemical functionalization when a molecule chemisorbs on a graphene layer via a single C–C (or other weakly Polar) Covalent Bond. The magnetic coupling between adsorbates shows a key dependence on the sublattice adsorption site. This effect is similar to that of H adsorption, however, with universal character. 3. The spin moment of substitutional metal impurities can be controlled using strain. In particular, we show that although Ni substitutionals are nonmagnetic in flat and unstrained graphene, the magnetism of these defects can be activated by applying either uniaxial strain or curvature to the graphene layer.
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First-Principles Study of the Electronic and Magnetic Properties of Defects in Carbon Nanostructures
arXiv: Mesoscale and Nanoscale Physics, 2013Co-Authors: Elton J. G. Santos, Andrés Ayuela, Daniel Sánchez-portalAbstract:Understanding the magnetic properties of graphenic nanostructures is instrumental in future spintronics applications. These magnetic properties are known to depend crucially on the presence of defects. Here we review our recent theoretical studies using density functional calculations on two types of defects in carbon nanostructures: Substitutional doping with transition metals, and sp$^3$-type defects created by Covalent functionalization with organic and inorganic molecules. We focus on such defects because they can be used to create and control magnetism in graphene-based materials. Our main results are summarized as follows: i)Substitutional metal impurities are fully understood using a model based on the hybridization between the $d$ states of the metal atom and the defect levels associated with an unreconstructed D$_{3h}$ carbon vacancy. We identify three different regimes, associated with the occupation of distinct hybridization levels, which determine the magnetic properties obtained with this type of doping; ii) A spin moment of 1.0 $\mu_B$ is always induced by chemical functionalization when a molecule chemisorbs on a graphene layer via a single C-C (or other weakly Polar) Covalent Bond. The magnetic coupling between adsorbates shows a key dependence on the sublattice adsorption site. This effect is similar to that of H adsorption, however, with universal character; iii) The spin moment of substitutional metal impurities can be controlled using strain. In particular, we show that although Ni substitutionals are non-magnetic in flat and unstrained graphene, the magnetism of these defects can be activated by applying either uniaxial strain or curvature to the graphene layer. All these results provide key information about formation and control of defect-induced magnetism in graphene and related materials.
Huan Ye - One of the best experts on this subject based on the ideXlab platform.
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First‐principles study of metal/nitride Polar interfaces: Ti/TiN
Surface and Interface Analysis, 2020Co-Authors: Shaoqing Wang, Huan YeAbstract:We have examined the optimal interface structure, ideal work of adhesion and Bonding character of Polar Ti(110)/TiN(111) interfaces by first-principles density-functional plane-wave pseudopotential calculations. Both Ti- and N-terminated interfaces, including six different interface structures, were calculated. The interface structure for each termination, continuing the TiN crystal structure across the interface, has the largest work of adhesion. Although both terminations yield substantial adhesion energies in the range 3-7 J m(-2), the N-terminated interface is similar to4 J m(-2) stronger than the Ti-terminated interface. Analysis of the interfacial electronic structure shows that the Ti-terminated interface is a mixed strong, metallic and weak Covalent character, whereas the N-terminated interface is a Polar Covalent Bond similar to the Ti/TiC interface. Further study of the separation of the optimal interface shows that the cleavages will never fracture at the interface due to the strong Bonding, which is consistent with the experimental results. Copyright (C) 2003 John Wiley Sons, Ltd.
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First-principles study of Polar Al/TiN(111) interfaces
Acta Materialia, 2004Co-Authors: S.q. Wang, Huan YeAbstract:This research purposes to investigate the optimal atomic structure, work of adhesion, electronic property and stability of Polar Al/TiN(1 1 1) interfaces by density functional theory. The results were then compared with non-Polar Al/TiN(0 0 1) interfaces. The outcome shows that the Polar interface structure which most resembles the ceramic stacking sequence across the interface has the strongest adhesion. Due to high surface energies, adhesion energies of Polar Al/TiN(1 1 1) interfaces are larger than those of Al/ TiN(0 0 1) interfaces. A thorough study of the electronic structure reveals that the N-terminated interface is the Polar Covalent Bond, and the Ti-terminated interface mainly shows the metallic Covalent interaction. The formation mechanism of interfacial AlN layer has also been well considered. Finally, thermodynamic examination shows that stabilities of both Polar TiN(1 1 1) surfaces and Al/ TiN(1 1 1) interfaces depend on the nitrogen chemical potential. This fact explains well the available experimental results. (C) 2004 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.