Single-crystal X-ray diffraction of BC8 carbon near terapascal pressures
Authors: Liang Sun, Bo Chen, Zhiyu He, Pin Yang, Zanyang Guan, Guo Jia, Fan Zhang, Yi Yang, Bo Xu, Pei Guo, Yonggang Liu, Wei Fan, Tao Xi, Yulong Li, Lingbiao Meng, Wei Kang, Zhiyong Xie, Yuqiong Tu, Cheng Ji, Xiuguang Huang, Zhongjing Chen, Ji Yan, Jiamin Yang, Wenge Yang, Toshimori Sekine, Zongqing Zhao, Jiayu Dai, Ho-Kwang Mao
Abstract
Whether carbon forms crystalline structures beyond diamond at terapascal pressures remains unresolved. Predicted for nearly four decades, the denser BC8 phase has lacked direct crystallographic evidence. Here we report the first direct crystallographic identification of BC8 carbon, formed as a single crystal from molten carbon during laser-driven decaying-shock compression of [100]-oriented diamond following loading above 1.1 TPa. Using in situ orientation-resolved single-crystal X-ray diffraction, we observe discrete Bragg spots whose spacings and angular relationships are reproduced by a common orientation matrix within each indexed BC8 reflection group, providing constraints beyond powder peak matching. Our single-crystal formation strategy and direct diffraction evidence resolve the decades-long quest for a post-diamond carbon structure, demonstrating how dynamic loading pathways can make predicted high-pressure phases experimentally accessible.
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Diamond melting and thermodynamic evidence for BC8 carbon at terapascal pressuresLiang Sun, Bo Chen, Huan Zhang et al. · 2026 · The Innovation · cited 1 time · Not summarized yet
Diamond melting and thermodynamic evidence for BC8 carbon examines whether BC8 forms from carbon near terapascal pressures.
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Extreme Metastability of Diamond and its Transformation to the BC8 Post-Diamond Phase of Carbon.K. Nguyen-Cong, J. T. Willman, Joseph M Gonzalez et al. · 2024 · Journal of Physical Chemistry Letters · cited 32 times · Not summarized yet
Extreme Metastability of Diamond and its Transformation to the BC8 Post-Diamond Phase of Carbon uses simulations to predict conditions where diamond can transform to BC8.
Abstract
Diamond possesses exceptional physical properties due to its remarkably strong carbon-carbon bonding, leading to significant resilience to structural transformations at very high pressures and temperatures. Despite several experimental attempts, synthesis and recovery of the theoretically predicted post-diamond BC8 phase remains elusive. Through quantum-accurate multimillion atom molecular dynamics (MD) simulations, we have uncovered the extreme metastability of diamond at very high pressures, significantly exceeding its range of thermodynamic stability. We predict the post-diamond BC8 phase to be experimentally accessible only within a narrow high pressure-temperature region of the carbon p…
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Double-Shock Compression Pathways from Diamond to BC8 Carbon.Jiu-Yang Shi, Zhi-Xin Liang, Jun-Jie Wang et al. · 2023 · Physical Review Letters · cited 28 times · Not summarized yet
Double-Shock Compression Pathways from Diamond to BC8 Carbon uses machine-learning-potential molecular dynamics to model routes to BC8, rather than identifying it by single-crystal diffraction.
Abstract
Carbon is one of the most important elements for both industrial applications and fundamental research, including life, physics, chemistry, materials, and even planetary science. Although theoretical predictions on the transition from diamond to the BC8 (Ia3[over ¯]) carbon were made more than thirty years ago, after tremendous experimental efforts, direct evidence for the existence of BC8 carbon is still lacking. In this study, a machine learning potential was developed for high-pressure carbon fitted from first-principles calculations, which exhibited great capabilities in modeling the melting and Hugoniot line. Using the molecular dynamics based on this machine learning potential, we desi…
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Diamond melting in shock compression experiments at 1 TPa pressuresM. Millot, F. Coppari, A. Lazicki et al. · 2026 · Nature Physics · cited 3 times · Not summarized yet
Diamond melting in shock compression experiments at 1 TPa pressures studies diamond melting under shock conditions relevant to the reported molten-carbon formation pathway.
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Pressure-Induced Interlayer Bonding in Arsenic Revealed by Single-Crystal Synchrotron X‑ray Diffraction in a Diamond Anvil CellM. Ceppatelli, M. Morana, Enrico Berretti et al. · 2026 · Journal of the American Chemical Society · Not summarized yet
Pressure-Induced Interlayer Bonding in Arsenic uses single-crystal X-ray diffraction under compression to resolve a pressure-induced structural change in another material.
Abstract
Arsenic was studied by single-crystal synchrotron X-ray diffraction during room T compression up to 37.8 GPa across the rhombohedral (As–I, A7) to simple cubic (As–II, sc) phase transition, using a diamond anvil cell for pressure generation and He as a pressure-transmitting medium. The pressure dependence of the rhombohedral lattice parameter a, angle α, atomic position parameter u, and first (d 1) and second (d 2) neighbor distances provides experimental evidence for a two-step pressure-induced interlayer bond formation mechanism, underlying the transition from the layered A7 structure to the nonlayered simple cubic one. Consistent with phosphorus, our data demonstrate the existence of an i…
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Towards a quantitative description of nanostructured order in amorphous diamond-like carbonA. Salek, Hendrik Heimes, E. Turner et al. · 2026 · Nature Communications · Not summarized yet
Towards a quantitative description of nanostructured order in amorphous diamond-like carbon studies compressed carbon, but characterizes non-crystalline structure rather than BC8.
Abstract
Our knowledge of crystals rests on precisely measured structural models, which are lacking for amorphous matter. Without long-range order, the available experimental evidence matches competing structural models, including paracrystalline and random network models, limiting our understanding of formation mechanisms and properties. This impedes discovery of new amorphous materials, including high-density sp³-rich carbons, among the hardest known. We show that the pair-angle distribution function (PADF) overcomes these limitations, applying it to a non-crystalline sp³-rich carbon produced by compression of fullerenes at room temperature. The PADF reveals that this phase contains nanostructures …
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Optical transitions in diamond at ultrahigh pressuresHo-kwang Mao, R. Hemley · 1991 · Nature · cited 88 times · Not summarized yet
Optical transitions in diamond at ultrahigh pressures concerns diamond’s behavior at high pressure, rather than identifying a post-diamond crystal structure.
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Maximizing completeness in single-crystal high-pressure diffraction experiments: phase transitions in 2°APD. Tchoń, A. Makal · 2021 · IUCrJ · cited 5 times · Not summarized yet
Maximizing completeness in single-crystal high-pressure diffraction experiments analyzes how sample orientation and DAC geometry affect the completeness of high-pressure diffraction data.
Abstract
The influence of a diamond anvil cell (DAC) aperture, incident radiation wavelength and sample orientation in a DAC on the completeness of diffraction data collected at high pressure has been systematically analyzed. The considerable impact of sample orientation on achievable data completeness has been confirmed and quantified for all Laue classes in the form of graphical guides. These guides have been applied to predict sample orientation for structural analysis of a sample undergoing an orthorhombic → monoclinic phase transition under pressure which ensured over 90% completeness.
Prior work it builds on
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Equation of state for boron nitride along the principal Hugoniot to 16 MbarHuan Zhang, Yutong Yang, Wei-Min Yang et al. · 2024 · Matter and Radiation at Extremes · cited 6 times · Not summarized yet
Equation of state for boron nitride along the principal Hugoniot to 16 Mbar reports shock-compression measurements at the same SGIII-p facility, but on boron nitride.
Abstract
The thermodynamic properties of boron nitride under extreme pressures and temperatures are of great interest and importance for materials science and inertial confinement fusion physics, but they are poorly understood owing to the challenges of performing experiments and realizing ab initio calculations. Here, we report the first shock Hugoniot data on hexagonal boron nitride at pressures of 5–16 Mbar, using hohlraum-driven shock waves at the SGIII-p laser facility in China. Our density functional theory molecular dynamics calculations closely match experimental data, validating the equations of state for modeling the shock response of boron nitride and filling a crucial gap in the knowledge…
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Stability and electronic properties of complex structures of silicon and carbon under pressure: Density-functional calculations.R. Biswas, Richard M. Martin, R. Needs et al. · 1987 · Physical Review B (Condensed Matter) · cited 61 times · Not summarized yet
Stability and electronic properties of complex structures of silicon and carbon under pressure uses density-functional calculations to study candidate high-pressure carbon structures.
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Machine learning interatomic potential for simulations of carbon at extreme conditionsJ. T. Willman, K. Nguyen-Cong, Ashley S Williams et al. · 2022 · Physical review B · cited 48 times · Not summarized yet
Machine learning interatomic potential for simulations of carbon at extreme conditions provides a validated carbon potential for simulating high-pressure phases and shock behavior.
Abstract
A Spectral Neighbor Analysis (SNAP) machine learning interatomic potential (MLIP) has been developed for simulations of carbon at extreme pressures (up to 5 TPa) and temperatures (up to 20,000 K). This was achieved using a large database of experimentally relevant quantum molecular dynamics (QMD) data, training the SNAP potential using a robust machine learning methodology, and performing extensive validation against QMD and experimental data. The resultant carbon MLIP demonstrates unprecedented accuracy and transferability in predicting the carbon phase diagram, melting curves of crystalline phases, and the shock Hugoniot, all within 3% of QMD. By achieving quantum accuracy and efficient im…
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Ramp compression of diamond to five terapascalsRaymond F. Smith, J. Eggert, R. Jeanloz et al. · 2014 · Nature · cited 225 times · Not summarized yet
Ramp compression of diamond to five terapascals studies diamond under extreme compression, but reports ramp loading rather than BC8 identification by shock diffraction.
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Carbon under extreme conditions: Phase boundaries and electronic properties from first-principles theoryA. Correa, S. Bonev, G. Galli · 2006 · Proceedings of the National Academy of Sciences of the United States of America · cited 211 times · Not summarized yet
Carbon under extreme conditions: Phase boundaries and electronic properties from first-principles theory calculates carbon phase boundaries and electronic properties relevant to high-pressure phase predictions.
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