The Melting Curve and Premelting of MgO

1996/05/03 by R. E. Cohen, Joshua S. Weitz, Cohen, R. E. +2 · 6 citations
Chemistry · Earth and Planetary Sciences · Engineering · Materials Science · Physics and Astronomy · #Chemistry #Composite material #FOS: Physical sciences #High-pressure geophysics and materials #Materials Science (cond-mat.mtrl-sci) #Materials science #Melting curve analysis #Melting point #Premelting #Thermodynamic and Structural Properties of Metals and Alloys #X-ray Diffraction in Crystallography #cond-mat.mtrl-sci #mtrl-th

paper · pdf · doi:10.48550/arxiv.mtrl-th/9605001

published in arXiv (Cornell University) (Cornell University) · Proceedings US Japan Seminar '96 High Pressure-Temperature Research: Properties of Earth and Planetary Materials, 17 pages plus 7 figures, latex, agums style (available from ftp://192.102.233.2/agutex/)

arxiv created 1996/05/03 · openalex publication_date 1996/05/03 · arxiv updated 2009/11/30 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05

Abstract

The melting curve for MgO was obtained using molecular dynamics and a non-empirical, many-body potential. We also studied premelting effects by computing the dynamical structure factor in the crystal on approach to melting. The melting curve simulations were performed with periodic boundary conditions with cells up to 512 atoms using the ab-initio Variational Induced Breathing (VIB) model. The melting curve was obtained by computing % ΔH_m and ΔV_m and integrating the Clapeyron equation. Our % ΔH_m is in agreement with previous estimates and we obtain a reasonable ΔV_m, but our melting slope dT/dP (114 K/GPa) is three times greater than that of Zerr and Boehler [1994] (35 K/GPa), suggesting a problem with the experimental melting curve, or an indication of exotic, non-ionic behavior of MgO liquid. We computed S(q,ω) from simulations of 1000 atom clusters using the Potential Induced Breathing (PIB) model. A low frequency peak in the dynamical structure factor % S(q,ω) arises below the melting point which appears to be related to the onset of bulk many-atom diffusive exchanges. These exchanges may help destabilize the crystalline state and be related to intrinsic crystalline instability suggested in earlier simulations.

Citations

• Explicit local exchange-correlation potentials
• On the use of windows for harmonic analysis with the discrete Fourier transform
• Self-Consistent Equations Including Exchange and Correlation Effects

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