Ternary Inorganic Compounds Containing Carbon, Nitrogen, and Oxygen at High Pressures

Steele, Brad A.; Oleynik, Ivan

doi:10.1021/acs.inorgchem.7b02102

Cited by 26 publications

(21 citation statements)

References 44 publications

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“…As at 500 GPa, this plane contains most stable or metastable ternary and quaternary phases. Along the edges, we find stable carbonic acid, H2CO3, ammonia hemihydrate (NH3)2 (H2O) and quarterhydrate (NH3)4 (H2O), cyanamide, CH2N2, carbon nitride imide, HC2N3, and oxycyanide, C2N2O, in agreement with literature (25,27,31). All are simple binary mixtures of the end members of this chemical subspace, forming in 1:1, 1:2, or 1:4 ratios.…”

supporting

confidence: 88%

Rules of formation of H–C–N–O compounds at high pressure and the fates of planetary ices

Conway

Pickard

Hermann

2021

Proc. Natl. Acad. Sci. U.S.A.

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The solar system’s outer planets, and many of their moons, are dominated by matter from the H–C–N–O chemical space, based on solar system abundances of hydrogen and the planetary ices H2O, CH4, and NH3. In the planetary interiors, these ices will experience extreme pressure conditions, around 5 Mbar at the Neptune mantle–core boundary, and it is expected that they undergo phase transitions, decompose, and form entirely new compounds. While temperature will dictate the formation of compounds, ground-state density functional theory allows us to probe the chemical effects resulting from pressure alone. These structural developments in turn determine the planets’ interior structures, thermal evolution, and magnetic field generation, among others. Despite its importance, the H–C–N–O system has not been surveyed systematically to explore which compounds emerge at high-pressure conditions, and what governs their stability. Here, we report on and analyze an unbiased crystal structure search among H–C–N–O compounds between 1 and 5 Mbar. We demonstrate that simple chemical rules drive stability in this composition space, which explains why the simplest possible quaternary mixture HCNO—isoelectronic to diamond—emerges as a stable compound and discuss dominant decomposition products of planetary ice mixtures.

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supporting

confidence: 88%

Rules of formation of H–C–N–O compounds at high pressure and the fates of planetary ices

Conway

Pickard

Hermann

2021

Proc. Natl. Acad. Sci. U.S.A.

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“…[8]. Several recent * dominika.melicherova@fmph.uniba.sk works investigated the possibility of creating and stabilizing single N-N bonds in systems other than pure nitrogen [9][10][11][12][13][14].…”

Section: Introductionmentioning

confidence: 99%

Structural evolution of amorphous polymeric nitrogen from ab initio molecular dynamics simulations and evolutionary search

Melicherová

Kohulák

Plašienka

et al. 2018

Phys. Rev. Materials

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Polymeric nitrogen with single bonds can be created from the molecular form at high pressure and due to large energy difference between triple and single bonds it is interesting as an energetic material. Its structure and properties are, however, still not well understood. We studied amorphous nitrogen by ab initio simulations, employing molecular dynamics and evolutionary algorithms. Amorphous nitrogen was prepared at a pressure of 120 GPa by quenching from a hot liquid, by pressure-induced amorphization of a molecular crystal, and by evolutionary search. All three amorphous forms were found to be structurally similar. We studied in detail the structural evolution of the system upon decompression from 120 GPa to zero pressure at 100 K. At pressures above 100 GPa, the system consists mainly of 3-coordinated atoms (80 %) connected by single bonds while some short chains made of 2-coordinated atoms are also present. Upon decompression, the number of 3-coordinated atoms rapidly decreases below 60 GPa and longer chains are created. At 20 GPa the system starts to create also N2 molecules and the ultimate structure at p = 0 contains molecules inside a polymeric network consisting dominantly of longer chains made of 2-coordinated atoms.Besides structure, we also study vibrational and electronic properties of the system and estimate the amount of energy that could be stored in amorphous nitrogen at ambient pressure. arXiv:1804.09072v2 [cond-mat.mtrl-sci]

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“…The superhardness effect was attributed to the strong electron localization into p-d orbital hybridization, induced by the N-N interstitial precompression. On the other hand, nitrogen-rich compounds have been considered as potential high-energy-density materials [16][17][18][19][20][21] . Recent theoretical predictions found that nitrogen can form rings at high pressure [19][20][21] .…”

mentioning

confidence: 99%

A novel superhard tungsten nitride predicted by machine-learning accelerated crystal structure search

Xia¹,

Gao²,

Liu³

et al. 2018

Science Bulletin

127

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Transition metal nitrides have been suggested to have both high hardness and good thermal stability with large potential application value, but so far stable superhard transition metal nitrides have not been synthesized. Here, with our newly developed machine-learning accelerated crystal structure searching method, we designed a superhard tungsten nitride, h-WN 6 , which can be synthesized at pressure around 65 GPa and quenchable to ambient pressure. This h-WN 6 is constructed with single-bonded N 6 rings and presents ionic-like features, which can be formulated as W 2.4+ N 6 2.4-. It has a band gap of 1.6 eV at 0 GPa and exhibits an abnormal gap broadening behavior under pressure. Excitingly, this h-WN 6 is found to be the hardest among transition metal nitrides known so far (Vickers hardness around 57 GPa) and also has a very high melting temperature (around 1900 K). These predictions support the designing rules and may stimulate future experiments to synthesize superhard material.

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Ternary Inorganic Compounds Containing Carbon, Nitrogen, and Oxygen at High Pressures

Cited by 26 publications

References 44 publications

Rules of formation of H–C–N–O compounds at high pressure and the fates of planetary ices

Rules of formation of H–C–N–O compounds at high pressure and the fates of planetary ices

Structural evolution of amorphous polymeric nitrogen from ab initio molecular dynamics simulations and evolutionary search

A novel superhard tungsten nitride predicted by machine-learning accelerated crystal structure search

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