Phase transitions of BaCO3 at high pressures
Phase transitions of BaCO3 at high pressures
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DOI：
10.1180/minmag.2008.072.2.659
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发表时间：
2008-04
影响因子：
2.7
通讯作者：
S. Ono;J. Brodholt;G. D. Price
中科院分区：
文献类型：
--
作者：
S. Ono;J. Brodholt;G. D. Price
摘要采用第一性原理模拟和高压实验研究了BaCO3碳酸盐在高压下的稳定性。毒重石，这是斜方晶系和同型碳酸钙文石，是在环境条件下稳定。随着压力的增加，BaCO3从毒重石转变为斜方晶后文石结构在8 GPa。计算得到的后文石结构的体积模量为60.7GPa，略小于实验值。该结构表现出轴向各向异性压缩性，a轴与caxis相交于70 GPa，这意味着以前实验研究中报道的压力诱导相变是错误的。虽然在压力>100 GPa时镁和钙碳酸盐中的辉石状结构是稳定的，但我们的模拟表明，这种结构不会出现在BaCO3中。
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 caxis 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.