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A lattice dynamical study of the aragonite and post-aragonite phases of calcium carbonate rock

type de publication      article dans une revue internationale avec comité de lecture
date de publication 2008
auteur(s) Sekkal W.; Taleb N.; Zaoui Ali; Shahrour Isam
journal (abréviation) American Mineralogist (Am Mineral)
volume (numéro) 93 (10)
pages 1608 – 1612
résumé A recent force field model is used in this paper to analyze, with a nano-scale simulation, the structural and the vibrational properties of a rock system under the application of various high pressures. Our results show that this model reproduces accurately the equilibrium structural properties for calcite, gives comparable results for aragonite with the observed data, and predicts the structural, elastic and vibrational properties of the post-aragonite phase. In addition, we show that the transition from the aragonite to the post-aragonite phase appears at a transition pressure of 35.2 GPa. The longitudinal wave velocity increases rapidly by a factor of 1.71. In contrast the shear wave velocity increases very slowly tip to the transition pressure, and thereafter increases rapidly, changing by 45% to 80 GPa. In addition, our calculations for the vibrational properties show that with the new potential model presented here, we observe a softening mode in the Gamma-F direction. The phonon frequencies of the post-aragonite phase show more modes than for calcite and aragonite.
mots clés Molecular dynamics, lattice dynamics, calcium carbonate rock
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