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

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{
  "metadata": {
    "is_last": true, 
    "version": 1, 
    "title": "Rules of formation of H\u2013C\u2013N\u2013O compounds at high pressure and the fates of planetary ices", 
    "keywords": [
      "H-C-N-O Chemistry", 
      "High Pressure", 
      "Ab Initio Random Structure Searching", 
      "Planetary Ices"
    ], 
    "description": "Results of an ab initio structure search on the H+C+N+O quaternary space at 500GPa.\n\nThe solar system\u2019s outer planets, and many of their moons, are dominated by matter from the H\u2013C\u2013N\u2013O 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\u2013core 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\u2019 interior structures, thermal evolution, and magnetic field generation, among others. Despite its importance, the H\u2013C\u2013N\u2013O 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\u2013C\u2013N\u2013O 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\u2014isoelectronic to diamond\u2014emerges as a stable compound and discuss dominant decomposition products of planetary ice mixtures.", 
    "license": "Creative Commons Attribution 4.0 International", 
    "references": [
      {
        "url": "https://doi.org/10.1073/pnas.2026360118", 
        "type": "Journal reference", 
        "citation": "L.J. Conway, C.J. Pickard, A. Hermann, PNAS 118 (19) (2021)", 
        "comment": "Paper in which the data is presented.", 
        "doi": "10.1073/pnas.2026360118"
      }, 
      {
        "url": "https://arxiv.org/abs/2011.13285", 
        "citation": "L.J. Conway, C.J. Pickard, A. Hermann, arXiv:2011.13285 [cond-mat.mtrl-sci]", 
        "type": "Preprint"
      }
    ], 
    "doi": "10.24435/materialscloud:p6-zh", 
    "conceptrecid": "816", 
    "publication_date": "Apr 12, 2021, 10:36:13", 
    "edited_by": 365, 
    "_oai": {
      "id": "oai:materialscloud.org:817"
    }, 
    "contributors": [
      {
        "affiliations": [
          "Centre for Science at Extreme Conditions, The University of Edinburgh, Edinburgh EH9 3FD, United Kingdom", 
          "School of Physics and Astronomy, The University of Edinburgh, Edinburgh EH9 3FD, United Kingdom"
        ], 
        "email": "l.j.conway@ed.ac.uk", 
        "familyname": "Conway", 
        "givennames": "Lewis J."
      }, 
      {
        "affiliations": [
          "Department of Materials Science & Metallurgy, University of Cambridge, Cambridge CB30FS, United Kingdom", 
          "Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan"
        ], 
        "email": "cjp20@cam.ac.uk", 
        "familyname": "Pickard", 
        "givennames": "Chris J."
      }, 
      {
        "affiliations": [
          "Centre for Science at Extreme Conditions, The University of Edinburgh, Edinburgh EH9 3FD, United Kingdom", 
          "School of Physics and Astronomy, The University of Edinburgh, Edinburgh EH9 3FD, United Kingdom"
        ], 
        "email": "a.hermann@ed.ac.uk", 
        "familyname": "Hermann", 
        "givennames": "Andreas"
      }
    ], 
    "owner": 365, 
    "license_addendum": null, 
    "mcid": "2021.62", 
    "_files": [
      {
        "size": 183533435, 
        "checksum": "md5:b93e134782225e78c19bc479208d16f1", 
        "description": "280,000+ structures generated by AIRSS and optimised by CASTEP at 500GPa. See README.", 
        "key": "HCNO-AIRSS.tar.gz"
      }, 
      {
        "size": 3176499, 
        "checksum": "md5:cb4e629ce3b9aa422df93bfb5531a225", 
        "description": "Optimised geometries of low energy structures between 20 and 700GPa. See README", 
        "key": "HCNO-Optimised.tar.gz"
      }, 
      {
        "size": 2765774, 
        "checksum": "md5:398de3f936ec8cd06ba6e888b1bd571b", 
        "description": "All data used in figures in the manuscript.", 
        "key": "Figs.tar.gz"
      }, 
      {
        "size": 2028, 
        "checksum": "md5:4184e30cfdb3d0080011fbcffb39f8f0", 
        "description": "README", 
        "key": "README.txt"
      }
    ], 
    "id": "817", 
    "status": "published"
  }, 
  "revision": 12, 
  "updated": "2021-05-19T14:15:34.607460+00:00", 
  "created": "2021-04-09T15:04:22.458928+00:00", 
  "id": "817"
}