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Phase transitions of BaCO3 at high pressures

Oxo, S; Brodholt, JP; Price, GD; (2008) Phase transitions of BaCO3 at high pressures. MINERAL MAG , 72 (2) 659 - 665. 10.1180/minmag.2008.072.2.659.

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Abstract

First-principles simulations and high-pressure experiments were used to study the stability of BaCO3 carbonates at high pressures. Witherite, which is orthorhombic and isotypic with CaCO3 aragonite, is stable at ambient conditions. As pressure increases, BaCO3 transforms from witherite to an orthorhombic post-aragonite structure at 8 GPa. The calculated bulk modulus of the post-aragonite structure is 60.7 GPa, which is slightly less than that from experiments. This structure shows an axial anisotropic compressibility and the a axis intersects with the c axis at 70 GPa, which implies that the pressure-induced phase transition reported in previous experimental study is misidentified. Although a pyroxene-like structure is stable in Mg- and Ca-carbonates at pressures >100 GPa, our simulations showed that this structure does not appear in BaCO3.

Type:Article
Title:Phase transitions of BaCO3 at high pressures
DOI:10.1180/minmag.2008.072.2.659
Keywords:BaCO3, phase transition, high pressure, ab initio calculation, AUGMENTED-WAVE METHOD, CRYSTAL-STRUCTURE, CACO3
UCL classification:UCL > School of BEAMS > Faculty of Maths and Physical Sciences > Earth Sciences
UCL > VP Research

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