Crystallography Reports

, 56:676 | Cite as

Lattice dynamics and the phase diagram of sodium at high pressures and temperatures from ab initio calculations

  • E. G. Maksimov
  • S. V. Lepeshkin
  • M. V. Magnitskaya
Lattice Dynamics and Phase Transitions

Abstract

The melting of sodium was investigated by two ab initio methods: (i) based on the calculations of the phonon spectra in the quasi-harmonic approximation with the use of the Lindemann criterion and (ii) by molecular-dynamics simulation. It is shown that the anomalous behavior of the melting curve Tm(p) for Na is explained well by the change in the phonon spectrum under compression; in particular, the decrease in Tm(p) at p > 30 GPa is due to the strong softening of transverse-phonon frequencies. The results obtained within both approaches are in good agreement and yield a reasonable quantitative description of the experimental melting curve of sodium at pressures up to ∼1 Mbar and temperatures from 300 to 1000 K. The good agreement between the two approaches indicates the smallness of anharmonicity effects in Na.

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Copyright information

© Pleiades Publishing, Ltd. 2011

Authors and Affiliations

  • E. G. Maksimov
    • 1
  • S. V. Lepeshkin
    • 2
  • M. V. Magnitskaya
    • 3
  1. 1.Lebedev Physical InstituteRussian Academy of SciencesMoscowRussia
  2. 2.Moscow Institute of Physics and Technology (State University)Dolgoprudnyi, Moscow oblastRussia
  3. 3.Institute for High Pressure PhysicsRussian Academy of SciencesTroitsk, Moscow oblastRussia

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