Metallic Carbon Allotrope Research Articles

QPHT-graphene: A new two-dimensional metallic carbon allotrope

A new two-dimensional metallic carbon allotrope (QPHT-graphene) composed by quadrangular, pentagonal, hexagonal rings, and large tetradecagonal pores, has been predicted based on the first-principles calculations. The total energy, phonon spectra, and elastic constants calculations as well as MD simulations prove that QPHT-graphene is a metastable carbon phase and can exist at room temperature. The calculations on the mechanical properties show that QPHT-graphene possesses an anisotropic mechanical behavior, and is much softer than graphene. Both GGA-PBE and HSE06 calculations confirm that QPHT-graphene is a metallic carbon allotrope with a much higher electronic density of states of ∼0.15 eV/states per atom at the Fermi level due to the emergence of flat bands. The current prediction further broadens the list of planar metastable carbon allotropes.

A new metallic carbon allotrope with high stability and potential for lithium ion battery anode material

Metallic carbon has been extensively studied for its potential novel applications in catalysis, superconductivity, and electronic devices. Currently, the design of metallic carbon is mainly by educated intuition which could miss some more stable allotropes. Here we carry out a global structure search on the potential energy surface, and identify a new three-dimensional (3D) metallic carbon phase, termed Hex-C18, which is energetically more favorable than most of the previously identified 3D metallic carbon allotropes. Using state-of-the-art theoretical calculations, we show that Hex-C18 not only possesses a high thermodynamic stability, large heat capacity, high Debye stiffness, anisotropic elasticity, and super hardness, but also is a promising anode material for lithium ion batteries (LIBs). As compared to graphite commercially used in LIBs, Hex-C18 exhibits a lower Li diffusion energy barrier and a higher Li capacity because of its intrinsic metallicity and regular porosity. In addition, the simulated x-ray diffraction of Hex-C18 matches well with a previously unidentified low-angle diffraction peak in experimental XRD spectra of detonation soot, implying the possibility of its existence in the specimen. This study expands the family of metallic carbon, and may open a new frontier in design of high performance anode materials for LIBs as well.

A planar carbon allotrope with linear bipentagon-octagon and hexagon arrangement

A two-dimensional (2D) metallic carbon allotrope is proposed, which consists of linearly aligned bipentagon-octagon and hexagon rings in a planar sheet. The relatively high percentage of hexagon and the regular arrangement of the polygons make it energetically more favorable than most of other predicted 2D carbon allotropes. Phonon dispersions without negative frequencies also indicate its stability. Electronic structure calculations show that its metallic nature is mainly due to the atoms shared by the pentagon, hexagon and octagon. Its lattice thermal conductivity is only about one fifth of that of graphene. Armchair- and zigzag-edged nanoribbons of this structure are also studied. The former is metallic while the latter has a small band gap due to the spin-polarized edge states. The appropriate band gap and the significantly reduced thermal conductivity suggest potential applications in thermoelectricity.

H18 Carbon: A New Metallic Phase with sp2-sp3 Hybridized Bonding Network.

Design and synthesis of three-dimensional metallic carbons are currently one of the hot issues in contemporary condensed matter physics because of their fascinating properties. Here, based on first-principles calculations, we discover a novel stable metallic carbon allotrope (termed H18 carbon) in () symmetry with a mixed sp2-sp3 hybridized bonding network. The dynamical stability of H18 carbon is verified by phonon mode analysis and molecular dynamics simulations, and its mechanical stability is analyzed by elastic constants, bulk modulus, and shear modulus. By simulating the x-ray diffraction patterns, we propose that H18 carbon would be one of the unidentified carbon phases observed in recent detonation experiments. The analysis of the band structure and density of states reveal that this new carbon phase has a metallic feature mainly due to the C atoms with sp2 hybridization. This novel 3D metallic carbon phase is anticipated to be useful for practical applications such as electronic and mechanical devices.

K 6 carbon: A metallic carbon allotrope in sp3 bonding networks

We identify by first-principles calculations a new cubic carbon phase in I4132 (O(8)) symmetry, named K6 carbon, which has a six atom primitive cell comprising sp(3) hybridized C3 triangle rings. The structural stability is verified by phonon mode analysis. The calculated elastic constants show that the K6 carbon is a high ductile material with a density even lower than graphite. Electronic band and density of states calculations reveal that it is a metallic carbon allotrope with a high electronic density of states of ∼0.10 states/eV per atom at the Fermi level. These results broaden our understanding of the structural and electronic properties of carbon allotropes.

A metallic carbon allotrope with superhardness: a first-principles prediction

From first-principles calculations, a novel carbon material with superhardness and metallicity is proposed and a possible endothermic transition is evaluated.

Prediction of a new two-dimensional metallic carbon allotrope

By means of the first-principles calculations, we predict a new metallic two-dimensional carbon allotrope named net W with Cmmm (D(2h)(19)) symmetry. This new carbon phase consists of squares C(4), hexagons C(6), and octagons C(8), its dynamical stability is validated based on phonon-mode analysis and it is energetically more favored over previously proposed two-dimensional carbon forms such as net C, planar C(4), biphenylene, graphyne, and the recently prepared graphdiyne. On the other hand, we find that net W possesses strong metallicity due to its rather large density of states across the Fermi level contributed by the carbon p(z) orbital. Through first-principles molecular dynamics simulations, we theoretically demonstrate that selective dehydrogenation of the parallel-laid narrowest angular polycyclic aromatic hydrocarbons (4-AGNRs) would lead to a spontaneous interconversion to such a net W carbon phase, the possible synthetic routes are also addressed. Of particular interest, semiconductivity could be introduced when a net W carbon sheet is cut into ribbons of certain widths. Our work shows that the net W carbon sheet and its nanoribbons have great potential for future nanoelectronics.