Superhard Monoclinic Polymorph of Carbon

Li, Quan; Ma, Yanming; Oganov, Artem R.; Wang, Hongbo; Wang, Hui; Xu, Ying; Cui, Tian; Mao, Ho‐kwang; Zou, Guangtian

doi:10.1103/physrevlett.102.175506

Cited by 526 publications

(356 citation statements)

References 30 publications

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“…When graphite is compressed under ambient temperature, x-ray IXS experiments showed that it undergoes a 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 transition at 17 GPa, where half of the π-bonds between graphite layers convert to σ-bonds, whereas the other half remain as π-bonds in the HP form [72]. The HP form has a distorted Mcarbon structure [661] and is super hard, capable of indenting cubic-diamond single crystals. Similarly, compressing fullerenes causes crushed C60 cages, forming superhard forms of carbon that are quenchable to ambient pressure [422,662].…”

Section: Superhard Materialsmentioning

confidence: 99%

High-pressure studies with x-rays using diamond anvil cells

2016

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Pressure profoundly alters all states of matter. The symbiotic development of ultrahighpressure diamond anvil cells, to compress samples to sustainable multi-megabar pressures; and synchrotron x-ray techniques, to probe materials' properties in situ, has enabled the exploration of rich high-pressure (HP) science. In this article, we first introduce the essential concept of diamond anvil cell technology, together with recent developments and its integration with other extreme environments. We then provide an overview of the latest developments in HP synchrotron techniques, their applications, and current problems, followed by a discussion of HP scientific studies using x-rays in the key multidisciplinary fields. These HP studies include: HP x-ray emission spectroscopy, which provides information on the filled electronic states of HP samples; HP x-ray Raman spectroscopy, which probes the HP chemical bonding changes of light elements; HP electronic inelastic x-ray scattering spectroscopy, which accesses high energy electronic phenomena, including electronic band structure, Fermi surface, excitons, plasmons, and their dispersions; HP resonant inelastic x-ray scattering spectroscopy, which probes shallow core excitations, multiplet structures, and spin-resolved electronic structure; HP nuclear resonant x-ray spectroscopy, which provides phonon densities of state and time-resolved Mössbauer information; HP x-ray imaging, which provides information on hierarchical structures, dynamic processes, and internal strains; HP x-ray diffraction, which determines the fundamental structures and densities of single-crystal, polycrystalline, nanocrystalline, and non-crystalline materials; and HP radial x-ray diffraction, which yields deviatoric, elastic and rheological information. Integrating these tools with hydrostatic or uniaxial pressure media, laser and resistive heating, and cryogenic cooling, has enabled investigations of the structural, vibrational, electronic, and magnetic properties of materials over a wide range of pressure-temperature conditions.

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Section: Superhard Materialsmentioning

confidence: 99%

High-pressure studies with x-rays using diamond anvil cells

2016

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“…XAS and EELS of graphene has been computed previously using density functional theory (DFT) implemented for ground-state electronic structure calculations [5,6]. These methods usually rely on periodic boundary conditions so that the asymptotic behavior of wavefunction may be not reproduced well for low-dimensional systems in particular directions, and use fixed basis sets whose convergence for high energy states may be problematic.…”

Section: Introductionmentioning

confidence: 99%

X-ray absorption spectra of graphene and graphene oxide by full-potential multiple scattering calculations with self-consistent charge density

Krüger

Natoli

et al. 2015

Phys. Rev. B

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X-ray absorption near edge structure (XANES) of graphene, graphene oxide and diamond are studied by the recently developed real-space full potential multiple scattering (FPMS) theory with space-filling cells. It is shown how accurate potentials for FPMS can be generated from self-consistent charge densities obtained with other schemes, especially the projector augmented wave method. Compared to standard multiple scattering calculations in the muffin-tin approximation, FPMS gives much better agreement with experiment. The effects of various structural modifications on the graphene spectra are well reproduced. (1) Stacking of graphene layers increases the peak intensity in the higher energy region. (2) The spectrum of the C atom located at the edge of graphene sheet shows a prominent pre-edge structure. (3) Adsorption of oxygen gives rise to the so-called interlayer-state peak. Moreover, O K-edge spectra of graphene oxide are calculated for three types of bonding, C-OH, C-O-C and C-O, and the proportions of these bondings at 800 • C are deduced by fitting them to the experimental spectrum.

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“…33 However, Mao et al find cold-compressing graphite leads to new superhard carbon allotropes differing from diamond. 34 A few candidates including R and P carbon, 20 bct C 4 , 26 W-C, 35 M-C, 36 and Z-C 37 have been proposed to match with the experimental results. Compressing CNTs yields more interesting but perplexing phases owing to the structural complexity of CNTs, such as chirality, diameter, single-wall or multi-wall.…”

Section: Introductionmentioning

confidence: 65%

Multiporous carbon allotropes transformed from symmetry-matched carbon nanotubes

Cai

Wang

et al. 2016

AIP Advances

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Carbon nanotubes (CNTs) with homogeneous diameters have been proven to transform into new carbon allotropes under pressure but no studies on the compression of inhomogeneous CNTs have been reported. In this study, we propose to build new carbon allotropes from the bottom-up by applying pressure on symmetry-matched inhomogeneous CNTs. We find that the (3,0) CNT with point group C3v and the (6,0) CNT with point group C6v form an all sp3 hybridized hexagonal 3060-Carbon crystal, but the (4,0) CNT with point group D4h and the (8,0) CNT with point group D8h polymerize into a sp2+sp3 hybridized tetragonal 4080-Carbon structure. Their thermodynamic, mechanical and dynamic stabilities show that they are potential carbon allotropes to be experimentally synthesized. The multiporous structures, excellently mechanical properties and special electronic structures (semiconductive 3060-Carbon and semimetallic 4080-Carbon) imply their many potential applications, such as gases purification, hydrogen storage and lightweight semiconductor devices. In addition, we simulate their feature XRD patterns which are helpful for identifying the two carbon crystals in future experimental studies.

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Superhard Monoclinic Polymorph of Carbon

Cited by 526 publications

References 30 publications

High-pressure studies with x-rays using diamond anvil cells

High-pressure studies with x-rays using diamond anvil cells

X-ray absorption spectra of graphene and graphene oxide by full-potential multiple scattering calculations with self-consistent charge density

Multiporous carbon allotropes transformed from symmetry-matched carbon nanotubes

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