Ab initio investigation of the melting line of molecular nitrogen at high pressure

ORAL

Abstract

Understanding the behavior of molecular systems under pressure is a fundamental problem in condensed matter physics. In the case of Nitrogen, the determination of the phase diagram and in particular of the melting line, are largely open problems. Two independent experiments have reported the presence of a maximum in the nitrogen melting curve, below 90 GPa, however the position and the interpretation of the origin of such maximum differ.By means of ab initio molecular dynamics simulations based on density functional theory and thermodynamic integration techniques, we have determined the phase diagram of nitrogen in the range between 20 and 100 GPa. We find a maximum in the melting line, connected to the presence of a triple point, which is related to a first order liquid-liquid phase transition, from molecular N$_2$ to polymeric nitrogen.

*Work supported by DOE/SciDAC DE-FC02-06ER25794

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Authors

  • Giulia Galli

    • Dept. of Chemistry and Dept. of Physics, UC Davis
    • Department of Chemistry and Department of Physics, University of California Davis
    • Dept of Chemistry \& Dept Physics, UC Davis
    • Department of Chemistry and Department of Physics, UC Davis, USA
    • Department of Chemistry and Department of Physics, University of California, Davis
    • UC Davis
    • Department of Chemistry, University of California, Davis, USA
    • University of California, Davis
    • Department of Chemistry and Department of Physics, University of California, Davis, CA, 95616
    • Department of Chemistry and Department of Physics, University of California, Davis, CA 95616
    • Chemistry Department and Physics Department UC Davis, Davis CA

  • Davide Donadio

    • Dept. Chemistry, UC Davis
    • Dept. of Chemistry, UC Davis
    • Department of Chemistry, UC Davis, USA

  • Leonardo Spanu

    • Department of Chemistry, University of California at Davis, Davis, 95616 CA
    • Dept. of Chemistry, UC Davis
    • Chemistry Department, UC Davis, Davis CA

  • Ivan Duchemin

    • University of California Davis
    • Dept. of Applied Science, UC Davis

  • Francois Gygi

    • Department of Applied Science and Department of Computer Science, University of California Davis
    • University of California Davis
    • Dept. Applied Science \& Dept. Computer Science, UC Davis
    • UC Davis
    • Dept. of Applied Science and Dept. of Computer Science, UC Davis