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Title: Carbon under extreme conditions: Phase boundaries and electronic properties from first-principles theory

Abstract

At high pressure and temperature, the phase diagram of elemental carbon is poorly known. We present predictions of diamond and BC8 melting lines and their phase boundary in the solid phase, as obtained from first-principles calculations. Maxima are found in both melting lines, with a triple point located at ≈ 850 GPa and ≈ 7,400 K. Our results show that hot, compressed diamond is a semiconductor that undergoes metalization upon melting. In contrast, in the stability range of BC8, an insulator to metal transition is likely to occur in the solid phase. Close to the diamond/liquid and BC8/liquid boundaries, molten carbon is a low-coordinated metal retaining some covalent character in its bonding up to extreme pressures. Lastly, our results provide constraints on the carbon equation of state, which is of critical importance for devising models of Neptune, Uranus, and white dwarf stars, as well as of extrasolar carbon-rich planets.

Authors:
 [1];  [2];  [3]
  1. Univ. of California, Berkeley, CA (United States); Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  2. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Dalhousie Univ., Halifax, NS (Canada)
  3. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Univ. of California, Davis, CA (United States)
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1348999
Report Number(s):
UCRL-JRNL-216286
Journal ID: ISSN 0027-8424
Grant/Contract Number:  
AC52-07NA27344
Resource Type:
Accepted Manuscript
Journal Name:
Proceedings of the National Academy of Sciences of the United States of America
Additional Journal Information:
Journal Volume: 103; Journal Issue: 5; Journal ID: ISSN 0027-8424
Publisher:
National Academy of Sciences, Washington, DC (United States)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; phase transitions; melting; high pressure; molecular dynamics; metalization

Citation Formats

Correa, Alfredo A., Bonev, Stanimir A., and Galli, Giulia. Carbon under extreme conditions: Phase boundaries and electronic properties from first-principles theory. United States: N. p., 2006. Web. doi:10.1073/pnas.0510489103.
Correa, Alfredo A., Bonev, Stanimir A., & Galli, Giulia. Carbon under extreme conditions: Phase boundaries and electronic properties from first-principles theory. United States. doi:10.1073/pnas.0510489103.
Correa, Alfredo A., Bonev, Stanimir A., and Galli, Giulia. Mon . "Carbon under extreme conditions: Phase boundaries and electronic properties from first-principles theory". United States. doi:10.1073/pnas.0510489103. https://www.osti.gov/servlets/purl/1348999.
@article{osti_1348999,
title = {Carbon under extreme conditions: Phase boundaries and electronic properties from first-principles theory},
author = {Correa, Alfredo A. and Bonev, Stanimir A. and Galli, Giulia},
abstractNote = {At high pressure and temperature, the phase diagram of elemental carbon is poorly known. We present predictions of diamond and BC8 melting lines and their phase boundary in the solid phase, as obtained from first-principles calculations. Maxima are found in both melting lines, with a triple point located at ≈ 850 GPa and ≈ 7,400 K. Our results show that hot, compressed diamond is a semiconductor that undergoes metalization upon melting. In contrast, in the stability range of BC8, an insulator to metal transition is likely to occur in the solid phase. Close to the diamond/liquid and BC8/liquid boundaries, molten carbon is a low-coordinated metal retaining some covalent character in its bonding up to extreme pressures. Lastly, our results provide constraints on the carbon equation of state, which is of critical importance for devising models of Neptune, Uranus, and white dwarf stars, as well as of extrasolar carbon-rich planets.},
doi = {10.1073/pnas.0510489103},
journal = {Proceedings of the National Academy of Sciences of the United States of America},
number = 5,
volume = 103,
place = {United States},
year = {2006},
month = {1}
}

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