The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Jiantao Wang - One of the best experts on this subject based on the ideXlab platform.
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a superhard Carbon Allotrope sc c46 Carbon
EPL, 2020Co-Authors: Chun-xiang Zhao, Chun-yao Niu, Jiaqi Wang, Yu Jia, Jiantao Wang, Caiping WangAbstract:The structural stabilities, mechanical and electronic properties of sc-C46 Carbon are systematically investigated by ab initio calculations. Our calculations reveal that the Vickers hardness (91 GPa) of sc-C46 Carbon is comparable to that of diamond and its ideal tensile and shear strength are 93 and 72 GPa, respectively. The sc-C46 Carbon is unveiled to be an insulator with a quasi-direct band gap of 5.11 eV. By simulating X-ray diffraction patterns, we propose that sc-C46 Carbon may be one of the unidentified Carbon phases in the detonation and chimney soot. These findings provide a solid footing for further exploration of the interesting properties and practical applications of sc-C46 Carbon.
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a new Carbon Allotrope with orthorhombic symmetry formed via graphitic sheet buckling
Physical Chemistry Chemical Physics, 2018Co-Authors: Jiantao WangAbstract:We identified by ab initio calculations a new simple orthorhombic Carbon Allotrope with Pmc21 (C2v2) symmetry that has a 32-atom unit cell in all-sp3 hybridized covalent bonds. This new Carbon phase can be formed from graphite via a one-layer by three-layer slip and buckling mechanism along the [210] direction above 7.16 GPa and is more favorable than previously proposed cold-compressed graphite phases such as Z-Carbon and M-Carbon in terms of both kinetics and energetics. Its dynamic stability has been confirmed by phonon mode analysis. Electronic band structure calculations reveal that it has a large indirect band gap of 5.91 eV, wider than that of diamond, which is expected to be optically transparent. The calculated hardness of 95.1 GPa is comparable to 97.5 GPa for diamond. These results offer insights into understanding the complex structural landscape of compressed graphite.
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topological nodal line semimetal in an orthorhombic graphene network structure
Physical Review B, 2018Co-Authors: Jiantao Wang, Yoshiyuki Kawazoe, Changfeng ChenAbstract:Topological semimetals are a fascinating class of quantum materials that possess extraordinary electronic and transport properties. These materials have attracted great interest in recent years for their fundamental significance and potential device applications. Currently a major focus in this research field is to theoretically explore and predict and experimentally verify and realize material systems that exhibit a rich variety of topological semimetallic behavior, which would allow a comprehensive characterization of the intriguing properties and a full understanding of the underlying mechanisms. In this paper, we report on ab initio calculations that identify a Carbon Allotrope with simple orthorhombic crystal structure in $Pbcm$ (${D}_{2h}^{11}$) symmetry. This Carbon Allotrope can be constructed by inserting zigzag Carbon chains between the graphene layers in graphite or by a crystalline modification of a (3,3) Carbon nanotube with a double cell reconstruction mechanism. Its dynamical stability has been confirmed by phonon and molecular dynamics simulations. Electronic band calculations indicate that it is a nodal-line semimetal comprising two nodal lines that go through the whole Brillouin zone in bulk and a projected surface flat band around the Fermi level. The present findings establish an additional topological semimetal system in the nanostructured Carbon Allotropes family and offer insights into its outstanding structural and electronic properties.
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computational prediction of a simple cubic Carbon Allotrope consisting of c12 clusters
Journal of Chemical Physics, 2017Co-Authors: Jiantao WangAbstract:We identify by ab initio calculations a new simple cubic Carbon phase in Pa3¯ symmetry, which has a 48-atom unit cell in all-sp3 bonding networks, thus termed SC48 Carbon. It can be viewed as a crystalline form of C12 clusters or a combined structure of SC24 and BC12 Carbon, but it is energetically more stable than the recently reported cubic Carbon phases such as BC8, SC24, BC12, and fcc-C12. The structural stability is verified by phonon mode analysis. Electronic band and density of state calculations reveal that SC48 Carbon is an insulator with a large direct band gap of 4.40 eV. Moreover, simulated x-ray diffraction patterns provide an excellent match to the distinct diffraction peaks found in milled fullerene soot. These results provide a solid foundation for further exploration of this new Carbon Allotrope.
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a new Carbon Allotrope with six fold helical chains in all sp 2 bonding networks
Scientific Reports, 2015Co-Authors: Jiantao Wang, Yoshiyuki Kawazoe, Changfeng Chen, Enge WangAbstract:Using a recently developed approach to constructing covalent network structures from linear carbyne, we identify by ab initio calculations a new Carbon Allotrope in R3m (D(3d)(5) symmetry that comprises six-fold helical chains with alternating sp(2)-type single and double bonds along the chains that are connected via zigzag benzene rings. This 6-fold carbene is characterized as a three-dimensional three-connected chiral crystalline modification of graphite. Phonon and electronic band calculations indicate that this new structure is dynamically stable and is a semiconductor with a band gap of 0.47 eV, in contrast to the semimetallic nature of graphite. Simulated x-ray diffraction patterns of the 6-fold carbene provide an excellent match to the previously unexplained distinct diffraction peak of a new Carbon Allotrope found in recent detonation experiments. These results establish a new Carbon phase and offer insights into its outstanding structural and electronic properties.
Yoshiyuki Kawazoe - One of the best experts on this subject based on the ideXlab platform.
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topological nodal line semimetal in an orthorhombic graphene network structure
Physical Review B, 2018Co-Authors: Jiantao Wang, Yoshiyuki Kawazoe, Changfeng ChenAbstract:Topological semimetals are a fascinating class of quantum materials that possess extraordinary electronic and transport properties. These materials have attracted great interest in recent years for their fundamental significance and potential device applications. Currently a major focus in this research field is to theoretically explore and predict and experimentally verify and realize material systems that exhibit a rich variety of topological semimetallic behavior, which would allow a comprehensive characterization of the intriguing properties and a full understanding of the underlying mechanisms. In this paper, we report on ab initio calculations that identify a Carbon Allotrope with simple orthorhombic crystal structure in $Pbcm$ (${D}_{2h}^{11}$) symmetry. This Carbon Allotrope can be constructed by inserting zigzag Carbon chains between the graphene layers in graphite or by a crystalline modification of a (3,3) Carbon nanotube with a double cell reconstruction mechanism. Its dynamical stability has been confirmed by phonon and molecular dynamics simulations. Electronic band calculations indicate that it is a nodal-line semimetal comprising two nodal lines that go through the whole Brillouin zone in bulk and a projected surface flat band around the Fermi level. The present findings establish an additional topological semimetal system in the nanostructured Carbon Allotropes family and offer insights into its outstanding structural and electronic properties.
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a new Carbon Allotrope with six fold helical chains in all sp 2 bonding networks
Scientific Reports, 2015Co-Authors: Jiantao Wang, Yoshiyuki Kawazoe, Changfeng Chen, Enge WangAbstract:Using a recently developed approach to constructing covalent network structures from linear carbyne, we identify by ab initio calculations a new Carbon Allotrope in R3m (D(3d)(5) symmetry that comprises six-fold helical chains with alternating sp(2)-type single and double bonds along the chains that are connected via zigzag benzene rings. This 6-fold carbene is characterized as a three-dimensional three-connected chiral crystalline modification of graphite. Phonon and electronic band calculations indicate that this new structure is dynamically stable and is a semiconductor with a band gap of 0.47 eV, in contrast to the semimetallic nature of graphite. Simulated x-ray diffraction patterns of the 6-fold carbene provide an excellent match to the previously unexplained distinct diffraction peak of a new Carbon Allotrope found in recent detonation experiments. These results establish a new Carbon phase and offer insights into its outstanding structural and electronic properties.
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Penta-graphene: A new Carbon Allotrope
Proceedings of the National Academy of Sciences, 2015Co-Authors: Shunhong Zhang, Jian Zhou, Yoshiyuki Kawazoe, Xiaoshuang Chen, Qian Wang, Puru JenaAbstract:A 2D metastable Carbon Allotrope, penta-graphene, composed entirely of Carbon pentagons and resembling the Cairo pentagonal tiling, is proposed. State-of-the-art theoretical calculations confirm that the new Carbon polymorph is not only dynamically and mechanically stable, but also can withstand temperatures as high as 1000 K. Due to its unique atomic configuration, penta-graphene has an unusual negative Poisson's ratio and ultrahigh ideal strength that can even outperform graphene. Furthermore, unlike graphene that needs to be functionalized for opening a band gap, penta-graphene possesses an intrinsic quasi-direct band gap as large as 3.25 eV, close to that of ZnO and GaN. Equally important, penta-graphene can be exfoliated from T12-Carbon. When rolled up, it can form pentagon-based nanotubes which are semiconducting, regardless of their chirality. When stacked in different patterns, stable 3D twin structures of T12-Carbon are generated with band gaps even larger than that of T12-Carbon. The versatility of penta-graphene and its derivatives are expected to have broad applications in nanoelectronics and nanomechanics.
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phase conversion from graphite toward a simple monoclinic sp3 Carbon Allotrope
Journal of Chemical Physics, 2012Co-Authors: Jiantao Wang, Changfeng Chen, Yoshiyuki KawazoeAbstract:We identify by ab initio calculations a simple monoclinic Carbon in P2/m (C2h1) symmetry with an alternating zigzag and armchair buckling of the Carbon sheets in AA stacking, which is formed via a distinct one-layer by one-layer conversion mechanism along the [210] direction assisted by a large lattice distortion. It is dynamically stable and energetically favorable as well as recently identified orthorhombic W- and monoclinic M-Carbon. Moreover, this new phase has a wider band gap than diamond's, and is compatible with the experimental x-ray diffraction data. These results broaden our understanding of the direct graphite-to-diamond phase transition.
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orthorhombic Carbon Allotrope of compressed graphite ab initio calculations
Physical Review B, 2012Co-Authors: Jiantao Wang, Yoshiyuki Kawazoe, Changfeng ChenAbstract:We identify by ab initio calculations an orthorhombic Carbon ($O$-Carbon) in $Pbam$ (${D}_{2h}^{9}$) symmetry for compressed graphite in AA stacking, which is formed via a distinct one-layer by one-layer slip and buckling mechanism along the [210] direction. It is dynamically stable and energetically more favorable than other known compressed graphite phases, albeit its slightly higher kinetic barrier. The $O$-Carbon is comparable to diamond in ultralow compressibility, has a band gap wider than that of diamond, and is compatible with experimental x-ray diffraction data. The present results offer insights for understanding the complex structural landscape of compressed graphite and the versatile nature of Carbon in forming a rich variety of structures under pressure.
Qian Wang - One of the best experts on this subject based on the ideXlab platform.
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a c20 based 3d Carbon Allotrope with high thermal conductivity
Physical Chemistry Chemical Physics, 2020Co-Authors: Yupeng Shen, Fancy Qian Wang, Jie Liu, Qian WangAbstract:Stimulated by the high thermal conductivity of diamond together with the light mass and rich resources of Carbon, a great deal of effort has been devoted to the study of the thermal conductivity of Carbon-based materials. In this work, we systematically study the thermal transport properties of a three dimensional (3D) C20 fullerene-assembled Carbon Allotrope, HSP3-C34, in which all Carbon atoms are in sp3 hybridization. The stability of HSP3-C34 is confirmed and its thermal conductivity is obtained by using first principles calculations combined with solving the linearized phonon Boltzmann transport equation. At room temperature, the thermal conductivity of HSP3-C34 is 731 W m−1 K−1, which is larger than those of many 3D Carbon Allotropes, such as BCO-C16 (452 W m−1 K−1), 3D graphene (150 W m−1 K−1) and T-Carbon (33 W m−1 K−1). A detailed analysis of its phonons reveals that three acoustic branches are the main heat carriers at room temperature, and the optical branches gradually become important with increasing temperature. A further study on the harmonic and anharmonic properties of HSP3-C34 uncovers that the main reasons for the high thermal conductivity are the weak anharmonicity and large group velocity resulting from the strong sp3 bonding. This study provides new insights on searching for Carbon Allotropes with high thermal conductivity.
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pcf graphene a 2d sp2 hybridized Carbon Allotrope with a direct band gap
Journal of Physical Chemistry C, 2019Co-Authors: Yiheng Shen, Junyi Liu, Yaguang Guo, Yu Qie, Qian WangAbstract:Motivated by the recent progress in synthesizing graphene by using aromatic benzene molecules as precursors, herein, we propose a new two-dimensional (2D) Carbon Allotrope by using nonaromatic molecule cyclooctatetraene as the precursor from a bottom-up approach. In this structure, all the Carbon atoms are threefold coordinated, similar to the sp2-hybridized atoms in graphene; thus, we name the poly-cyclooctatetraene framework as PCF-graphene. First-principles calculations reveal that although PCF-graphene is metastable compared with graphene, it is thermally, mechanically, and dynamically stable. Different from graphene with a single-atomic thickness and zero band gap, PCF-graphene has a finite thickness of 2.45 A and is a semiconductor with a direct band gap of 0.77 eV. It exhibits anisotropies in mechanical properties, carrier mobility, and optical adsorption because of its anisotropic lattice. This study not only sheds insights into the design of 2D Carbon materials from some simple organic molecules ...
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PCF-Graphene: A 2D sp2‑Hybridized Carbon Allotrope with a Direct Band Gap
2019Co-Authors: Yiheng Shen, Junyi Liu, Yaguang Guo, Yu Qie, Qian WangAbstract:Motivated by the recent progress in synthesizing graphene by using aromatic benzene molecules as precursors, herein, we propose a new two-dimensional (2D) Carbon Allotrope by using nonaromatic molecule cyclooctatetraene as the precursor from a bottom-up approach. In this structure, all the Carbon atoms are threefold coordinated, similar to the sp2-hybridized atoms in graphene; thus, we name the poly-cyclooctatetraene framework as PCF-graphene. First-principles calculations reveal that although PCF-graphene is metastable compared with graphene, it is thermally, mechanically, and dynamically stable. Different from graphene with a single-atomic thickness and zero band gap, PCF-graphene has a finite thickness of 2.45 Å and is a semiconductor with a direct band gap of 0.77 eV. It exhibits anisotropies in mechanical properties, carrier mobility, and optical adsorption because of its anisotropic lattice. This study not only sheds insights into the design of 2D Carbon materials from some simple organic molecules but also expands the 2D purely three-coordinated Carbon family from a single-atomic layer to a finite thickness. PCF-graphene can be used as a rung in the ladder to stabilize three-dimensional three-coordinated Carbon system that remains elusive currently
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Penta-graphene: A new Carbon Allotrope
Proceedings of the National Academy of Sciences, 2015Co-Authors: Shunhong Zhang, Jian Zhou, Yoshiyuki Kawazoe, Xiaoshuang Chen, Qian Wang, Puru JenaAbstract:A 2D metastable Carbon Allotrope, penta-graphene, composed entirely of Carbon pentagons and resembling the Cairo pentagonal tiling, is proposed. State-of-the-art theoretical calculations confirm that the new Carbon polymorph is not only dynamically and mechanically stable, but also can withstand temperatures as high as 1000 K. Due to its unique atomic configuration, penta-graphene has an unusual negative Poisson's ratio and ultrahigh ideal strength that can even outperform graphene. Furthermore, unlike graphene that needs to be functionalized for opening a band gap, penta-graphene possesses an intrinsic quasi-direct band gap as large as 3.25 eV, close to that of ZnO and GaN. Equally important, penta-graphene can be exfoliated from T12-Carbon. When rolled up, it can form pentagon-based nanotubes which are semiconducting, regardless of their chirality. When stacked in different patterns, stable 3D twin structures of T12-Carbon are generated with band gaps even larger than that of T12-Carbon. The versatility of penta-graphene and its derivatives are expected to have broad applications in nanoelectronics and nanomechanics.
Rui Wang - One of the best experts on this subject based on the ideXlab platform.
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photoinduced floquet mixed weyl semimetallic phase in a Carbon Allotrope
Physical Review B, 2020Co-Authors: Tingwei Deng, Baobing Zheng, Fangyang Zhan, Jing Fan, Rui WangAbstract:The interplay between light and matter attracts tremendous interest for exploring novel topological quantum states and their phase transitions. Here we show by first-principles calculations and the Floquet theorem that a Carbon Allotrope body-centered tetragonal ${\text{C}}_{16}$ $(\mathrm{bct}\text{\ensuremath{-}}{\mathrm{C}}_{16})$, a typical nodal-line semimetal, exhibits exotic photoinduced Floquet mixed-Weyl semimetallic features. Under the irradiation of a linearly polarized light, $\mathrm{bct}\text{\ensuremath{-}}{\mathrm{C}}_{16}$ undergoes a topological phase transition from a nodal-line semimetal to a Weyl semimetal with two pairs of tunable Weyl points. With increasing the light intensity, left-handed Weyl points evolve from type I into type II while right-handed ones are always preserved to be type I, giving rise to light-induced unconventional Weyl pairs composed of distinct types of Weyl points. Importantly, a special Weyl pair formed by type-I and type-III Weyl points is present at the critical transition point. The photon-dressed Fermi arcs connecting the projections of two different types of Weyl points are clearly visible, further revealing their unique topological features. Our work not only realizes promising unconventional Weyl pairs but also paves a reliable avenue for investigating light-induced topological phase transitions.
F M Peeters - One of the best experts on this subject based on the ideXlab platform.
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pai graphene a new topological semimetallic two dimensional Carbon Allotrope with highly tunable anisotropic dirac cones
Carbon, 2020Co-Authors: Xin Chen, Adrien Bouhon, F M Peeters, Biplab SanyalAbstract:Abstract Using evolutionary algorithm for crystal structure prediction, we present a new stable two-dimensional (2D) Carbon Allotrope composed of polymerized as-indacenes (PAI) in a zigzag pattern, namely PAI-graphene whose energy is lower than most of the reported 2D Allotropes of graphene. Crucially, the crystal structure realizes a nonsymmorphic layer group that enforces a nontrivial global topology of the band structure with two Dirac cones lying perfectly at the Fermi level. The absence of electron/hole pockets makes PAI-graphene a pristine crystalline topological semimetal having anisotropic Fermi velocities with a high value of 7.0 × 10 5 m/s. We show that while the semimetallic property of the Allotrope is robust against the application of strain, the positions of the Dirac cone and the Fermi velocities can be modified significantly with strain. Moreover, by combining strain along both the x- and y-directions, two band inversions take place at Γ leading to the annihilation of the Dirac nodes demonstrating the possibility of strain-controlled conversion of a topological semimetal into a semiconductor. Finally we formulate the bulk-boundary correspondence of the topological nodal phase in the form of a generalized Zak-phase argument finding a perfect agreement with the topological edge states computed for different edge-terminations.
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t4 4 4 graphyne a 2d Carbon Allotrope with an intrinsic direct bandgap
Solid State Communications, 2019Co-Authors: F M Peeters, Weiyang Wang, Xiangru Kong, B Van DuppenAbstract:Abstract A novel two-dimensional (2D) structurally stable Carbon Allotrope is proposed using first-principles calculations, which is a promising material for water purification and for electronic devices due to its unique porous structure and electronic properties. Rectangular and hexagonal rings are connected with acetylenic linkages, forming a nanoporous structure with a pore size of 6.41 A, which is known as T4,4,4-graphyne. This 2D sheet exhibits a direct bandgap of 0.63 eV at the M point, which originates from the pz atomic orbitals of Carbon atoms as confirmed by a tight-binding model. Importantly, T4,4,4-graphyne is found to be energetically more preferable than the experimentally realized β-graphdiyne, it is dynamically stable and can withstand temperatures up to 1500 K.