Query: T-carbon:  a  novel  carbon  allotrope

Candidate papers:

abstract: A structurally stable crystalline carbon allotrope is predicted by means of the first principles calculations. This allotrope can be derived by substituting each atom in diamond with a carbon tetrahedron, and possesses the same space group Fd3m as diamond, which is thus coined as T carbon. The calculations on geometrical, vibrational, and electronic properties reveal that T carbon, with a considerable structural stability and a much lower density 1.50 g/cm3, is a semiconductor with a direct band gap about 3.0 eV, and has a Vickers hardness 61.1 GPa lower than diamond but comparable with cubic boron nitride. Such a form of carbon, once obtained, would have wide applications in photocatalysis, adsorption, hydrogen storage, and aerospace materials.
author_names: Xian-Lei Sheng

Qing-Bo Yan

Fei Ye

Qing-Rong Zheng

Gang Su
title: T carbon: a novel carbon allotrope.
venue: Physical review letters
year: 2011

abstract: Abstract A novel carbon allotrope, denoted P2/m C54, is proposed in this work. The structural properties, mechanical properties, mechanical and dynamical stability, relative formation enthalpy, anisotropy in Young's modulus and electronic properties for P2/m C54 are investigated in this work. First, P2/m C54 is found to remain mechanically and dynamically stable below 100 GPa, with a relative formation enthalpy that is 0.729 eV/atom less than that of T carbon. The bulk modulus, shear modulus and Young's modulus of P2/m C54 are calculated to be 345 GPa, 332 GPa and 754 GPa, respectively; the hardness of P2/m C54 is calculated to be 54.1 GPa and 70.4 GPa using Chen's model and Lyakhov and Oganov's model, respectively. All these calculations suggest that P2/m C54 is a potential superhard material. Furthermore, the band gap of P2/m C54 is determined to be 4.95 eV; in other words, P2/m C54 is an indirect band gap semiconductor material with a wide band gap at ambient pressure.
author_names: Xiaozhen Li

Mengjiang Xing
title: Prediction of a novel carbon allotrope from first principle calculations: A potential superhard material in monoclinic symmetry
year: 2020

abstract: Through first principles calculations, we predict a new superhard carbon allotrope named C 20 T, which possesses a cubic T symmetry with space group No.198(P213) This new carbon allotrope has an all sp (3) hybridized bonding network with 20 atoms in its primitive unit cell. The dynamic, mechanical, and thermal stabilities of this new carbon phase at zero pressure are confirmed by using a variety of state of the art theoretical calculations. Interestingly, despite the fact that C 20 T carbon has a porous structure with large cavities, our calculations identify its superhard properties with the Vickers hardness of 72.76 Gpa. The ideal tensile and shear strength of C 20 T carbon are calculated to be 71.1 and 55.2 GPa respectively, comparable to that of c BN. Electronic band calculations reveal that this new carbon allotrope is a transparent insulator with an indirect band gap of 5.44 eV. These results broaden our understanding of superhard carbon allotropes.
author_names: Jia-Qi Wang

Chunxiang Zhao

Chunyao Niu

Qiang Sun

Yu Jia
title: C 20 T carbon: a novel superhard sp (3) carbon allotrope with large cavities.
venue: Journal of physics. Condensed matter an Institute of Physics journal
year: 2016

abstract: By means of ab initio computations and the global minimum structure search method, we have investigated structural, mechanical, and electronic properties of D carbon, a crystalline orthorhombic sp3 carbon allotrope (space group Pmma D2h5 with 6 atoms per cell) Total energy calculations demonstrate that D carbon is energetically more favorable than the previously proposed T6 structure (with 6 atoms per cell) as well as many others. This novel phase is dynamically, mechanically, and thermally stable at zero pressure and more stable than graphite beyond 63.7 GPa. D carbon is a semiconductor with a bandgap of 4.33 eV, less than diamond's gap (5.47 eV) The simulated X ray diffraction pattern is in satisfactory agreement with previous experimental data in chimney or detonation soot, suggesting its possible presence in the specimen.
author_names: Dong Fan

Shaohua Lu

Andrey A Golov

Artem A Kabanov

Xiaojun Hu
title: D carbon: Ab initio study of a novel carbon allotrope.
venue: The Journal of chemical physics
year: 2018

abstract: A novel cubic porous carbon allotrope C96 carbon with intriguing physical properties was predicted. It has 96 atoms in the conventional cell, possessing a Pmm space group. The basic building block of C96 carbon is a planar six membered carbon ring. The structural stability, mechanical properties, and dynamical properties of C96 carbon were extensively studied. It is a semiconductor (1.85 eV) with a lower density (2.7 g cm 3) and a larger bulk modulus (279 GPa) and is stable under ambient conditions. The hardness of C96 carbon (25 GPa) is larger than that of T carbon (5.6 GPa) Due to the structural porous feature and lower density, C96 carbon can also be expected to be a good hydrogen storage material.
author_names: Da Li

Fubo Tian

Binhua Chu

Defang Duan

Shuli Wei

Yunzhou Lv

Huadi Zhang

Lu Cai Wang

Nan Lu

Bingbing Liu

Tian Cui
title: Cubic C96: a novel carbon allotrope with a porous nanocube network
year: 2015

abstract: Abstract Based on density functional theory, a novel carbon allotrope in the Pm 3m space group with cubic symmetry (denoted as cP144 carbon below) is proposed in this work; the conventional cell of the allotrope contains 144 carbon atoms, and its structural properties, mechanical anisotropy properties, electronic properties, and mechanical properties are also predicted. The cP144 carbon is dynamically and mechanically stable, and the related enthalpy of cP144 carbon is smaller than that of T carbon, Y carbon, TY carbon, TII carbon, YII carbon and TYII carbon. cP144 carbon is a carbon material with a microporous structure, and the maximum distance of the microporous structure is 12.172 A together with a minimum distance of 9.918 A. cP144 carbon may be used for hydrogen and lithium storage materials. The electronic band structure calculations showed that cP144 carbon is a direct band gap semiconductor material with a band gap of 0.34 eV; such a material can also be considered a photoelectric material. The density of cP144 (1.149 g/cm3) is only approximately two thirds that of T carbon. The bulk modulus of cP144 carbon is 101 GPa higher than that of Y carbon and TY carbon.
author_names: Qingyang Fan

Yingxiu Zhao

Xinhai Yu

YanXing Song

Wei Zhang

Sining Yun
title: Physical properties of a novel microporous carbon material
year: 2020

abstract: A novel allotrope of carbon with P2/m symmetry was identified during an ab initio minima hopping structural search which we call M10 carbon. This structure is predicted to be more stable than graphite at pressures above 14.4 GPa and consists purely of sp3 bonds. It has a high bulk modulus and is almost as hard as diamond. A comparison of the simulated X ray diffraction pattern shows a good agreement with experimental results from cold compressed graphite.
author_names: Maximilian Amsler

Jose A Flores-Livas

Miguel A L Marques

Silvana Botti

Stefan Goedecker
title: Prediction of a novel monoclinic carbon allotrope
year: 2012

abstract: Owing to the various ways of chemical bonding, carbon can form abundant allotropes with different frameworks, which harbor rich mechanical and electronic properties. Taking the cage like isomer of C16cluster as building block, we design a new low density carbon allotrope, which has the tetragonal symmetry (I4/mmm) and a 56 atoms unit cell, hence termed as T C56. Our first principles calculations reveal that T C56is not only energetically, dynamically, thermally (above 1800 K) and mechanically stable, but even more stable than the experimentally synthesized C20 sc and T carbon. Remarkably, although the framework of T C56is low density (2.72g/cm3) it exhibits novel superhard properties with a Vickers hardness of 48.71 GPa. The obtained Yang's modulus and ideal strength shows that T C56is mechanically anisotropic. In particular, our analysis of electronic and optical properties suggest that T C56is a transparent indirect semiconductor with a wide bandgap of 3.18 eV (HSE06) These findings highlight a distinct carbon allotrope, having promising applications for optical and aerospace devices due to its light, transparent, superhard features.
author_names: Yanqing Guo

Leyuan Cui

Ding Zhao

T L Song

Xin Cui

Zhifeng Liu
title: T C56: A low density transparent superhard carbon allotrope assembled from C16 cage like cluster.
venue: Journal of physics. Condensed matter an Institute of Physics journal
year: 2020

abstract: A novel allotrope of carbon with P2/m symmetry was identified during an ab initio minimahopping structural search which we call M10 carbon. This structure is predicted to be more stable than graphite at pressures above 14.4 GPa and consists purely of sp bonds. It has a high bulk modulus and is almost as hard as diamond. A comparison of the simulated X ray diffraction pattern shows a good agreement with experimental results from cold compressed graphite. Graphite and diamond are the thermodynamically most stable forms of carbon at ambient conditions. However, carbon can be found in a vast structural variety due to its flexibility to form sp spand sphybridized bonds: hexagonal diamond, nano diamond, carbon foams, fullerenes and nanotubes are just some examples of known carbon allotropes. Experimental evidences of a novel super hard carbon phase have been reported in literature when graphite is compressed at room temperatures. Changes in resistivity [1] optical transmittance [2,3] optical reflectivity [4] X ray diffraction (XRD) patterns [5 7] and in the raman spectra [8,9] indicate a phase transition in the range of 10 to 25GPa. Recently, several candidate structures have been proposed to match these experimental observations [10] such as M carbon [11] bct C4 carbon [12] W carbon [13] and Z carbon [8,14] Although Z carbon is thermodynamically the most promising structure, a final and conclusive determination has not yet been possible. In this article we report on a novel carbon allotrope discovered with the recently developed minima hopping crystal structure prediction method (MHM) [15,16] The MHM is capable to predict the most stable and metastable structures given solely the chemical composition of a system. Short molecular dynamics simulations are used to escape from local minima, and local geometry relaxations are performed to identify stable configurations. High efficiency of the escape step is ensured by aligning the initial molecular dynamics velocities along soft mode directions, and revisiting already explored regions of the potential energy surface is avoided by a feedback mechanism. The minima hopping method has been successfully used in a wide range of applications [8,17 21] a e mail: silvana.botti@univ lyon1.fr b e mail: stefan.goedecker@unibas.ch During our MHM simulations, the energies and the Hellman Feynman forces were evaluated at the density functional theory (DFT) level within the local density approximation (LDA) and the all electron projectoraugmented wave method was employed as implemented in the abinit code [22,23] The most promising structures were further relaxed using norm conserving HartwigsenGoedecker Hutter (HGH) pseudopotentials [24] The total energy was converged within less than 1 meV per atom by a plane wave cut off energy of 2100 eV and well converged Monkhorst Pack k point meshes. We reconfirmed the energy ordering with two other exchangecorrelation functionals within the generalized gradient approximation, namely PBE [25] and PBEsol [26] Several MHM simulations were carried out with cells containing up to 8 atoms at 15 GPa within an unconstrained and thorough structural search, starting from different input configurations. We identified a novel, monoclinic carbon phase with P2/m symmetry, which we call M10 carbon. It consists solely of sp bonds and contains 8 atoms per cell. At ambient pressure, the unit cell parameters are given by a 4.080 A, b 2.498 A, c 4.728 A, a g 90* and b 73.96* Two carbon atoms each occupy the crystallographic 2n sites at 0.1, 0.5, 0.113) and 0.132, 0.5, 0.421) and the 2m sites at 0.333, 0, 0.466) and 0.325, 0, 0.117) The overall structure is closely related to M carbon, also consisting of 5and 7 membered rings along the b axis, while 6 membered rings are formed along the c axis. In contrast to M carbon, the 5 rings share the long edge, whereas in M10 carbon they share the short edge. The structure is illustrated in Figure 1. The dynamical stability was investigated by analyzing the phonon dispersion within the whole Brillouin zone. Density functional perturbation theory [27] as Page 2 of 3 Eur. Phys. J. B (2013) 86: 383 Fig. 1. The structure of M10 carbon from two different angles. The left panel shows the 5and 7 membered rings, while the right panel reveals the 6 membered rings. 200 100 0 100 200 300 0 5 10 15 20 25 D m eV Pressure (GPa) Graphite bct C4 M carbon W carbon Hex diamond Cub diamond Z carbon M10 carbon Fig. 2. Enthalpy differences per atom with respect to graphite of several carbon allotropes are shown as a function of pressure. The most promising candidate is Z carbon since it crosses the graphite line at roughly 10 GPa. However, M10 carbon becomes thermodynamically accessible above 14.4 GPa. implemented in abinit, was employed with a 12x12x12 k point sampling and a 4 x 4 x 4 q point mesh. No imaginary phonon frequencies were found, confirming the lattice stability of the phase. The thermodynamical stability of M10 carbon was investigated by computing its enthalpy within a wide pressure range. In Figure 2, the enthalpies of all proposed candidates for cold compressed graphite are plotted with respect to graphite as a function of pressure, neglecting the zero point vibrational energies. M10 carbon becomes enthalpically favorable over graphite above a pressure of 14.4 GPa. As expected from the structural similarities with M carbon, both M10and M carbon are very close in enthalpy throughout the whole pressure range with an enthalpy difference of merely 3.9 meV/atom at 15 GPa. The vibrational contribution to the free energy within the harmonic approximation at 300 K reduces this value insignificantly by 0.003 meV/atom. In Table 1, we compare the structural properties of M10 carbon with other carbon allotropes. The bulk moduli B0 were computed using the Murnaghan equation, and the Vickers hardnesses Hv were estimated with the method of Gao et al. [28] Like all of the investigated Table 1. Calculated and experimental data (where available) of the bulk moduli B0 (in GPa) Vickers Hardness Hv (in GPa) and volumes per atom V0 (in A /atom) at 0 GPa for bct C4, M W Z M10 carbon and diamond. Structure Method B0 (GPa) Hv (GPa) V0 (A) bct C4 this work 428.2 93.5 5.82 LDA [13] 433.7 5.83 M carbon this work 428.4 93.9 5.77 LDA [11] 431.2 83.1 5.78 W carbon this work 427.5 94.2 5.75 LDA [13] 444.5 5.76 Cub diamond this work 463.0 97.8 5.51 LDA [13] 466.3 5.52 Expt. 446 60 120b 5.67 Z carbon LDA [8] 441.5 95.4 5.66 M10 carbon this work 423.7 93.5 5.79 a Reference [29] b reference [30] Fig. 3. The simulated XRD patterns are compared with the experimental results from reference [7] of cold compressed graphite. While at 13.7 GPa graphite was used to compute the simulated XRD pattern, M10 carbon was used for the simulation at 23.9 GPa. structures, M10 carbon is nearly as hard as diamond and has a very high bulk modulus, which could well account for ring cracks in diamond anvil cells [7] Furthermore, an analysis of the electronic band tructure was carried out, showing that M10 carbon is a wide band gap semiconductor with an indirect PBE gap of 4.4 eV at 0 GPa. Finally, we compare the XRD pattern of M10 carbon to experimental measurements from reference [7] as illustrated in Figure 3. The simulated pattern gives a good match to the experimental spectrum and could well explain the observed changes. It can, therefore, be expected that M10 carbon is present in samples of coldcompressed graphite above 14.4 GPa. However, other carbon allotropes show a similarly good agreement and thus the XRD pattern alone is by no way a conclusive evidence. In conclusion, we present a novel carbon allotrope that we call M10 carbon. It is a transparent, super hard material which becomes enthalpically favorable over Eur. Phys. J. B (2013) 86: 383 Page 3 of 3 graphite at pressures above 14.4 GPa. Both the structural and enthalpical properties are very similar to the previously proposed M carbon [11] The XRD pattern is in good agreement with experimental measurements, and although other carbon allotropes are enthalpically preferred at lower pressures, it could well be synthesized in samples of cold compressed graphite. Financial support provided by the Swiss National Science Foundation is gratefully acknowledged. Computational resources were provided by the Swiss National Supercomputing Center (CSCS) in Lugano and IDRIS GENCI (project x2012096017) in France.
author_names: Maximilian Amsler

Jose A Flores-Livas

Miguel A L Marques

Silvana Botti

Stefan Goedecker
title: THE EUROPEAN PHYSICAL JOURNAL B Prediction of a novel monoclinic carbon allotrope
year: 2013

abstract: A novel stable carbon allotrope is predicted by using first principles calculations. This allotrope is obtained by replacing one of the two atoms in the primitive cell of diamond with a carbon tetrahedron, thus it contains five atoms in one primitive cell, termed T5 carbon. The stabilities of T5 carbon are checked in structural, thermal, vibrational and energy calculations. The calculations on electronic, thermal, and mechanical properties reveal that T5 carbon is a semiconductor with an indirect band gap of 3.18 eV, and has a lattice thermal conductivity of 409 W/mK. More importantly, the Vickers hardness of T5 carbon is 76.5 GPa which is lower than that of diamond but larger than those of T carbon and cubic boron nitride, confirming the superhard properties of T5 carbon, suggesting its wide applications in mechanical devices.
author_names: Xian-Yong Ding

Chao Zhang

Dong-qi Wang

Bingsheng Li

Qingping Wang

Zhi Gen Yu

Kah-Wee Ang

Yong-Wei Zhang
title: A potential superhard carbon allotrope: T5 carbon
year: 2020