Elastic properties of CaCO3 high pressure phases from first principles

• Published in: 中国物理B：英文版 Vol. 26; no. 8; pp. 587 - 594
• Main Author: 黄丹 刘红 侯明强 谢梦雨 鹿亚飞 刘雷 易丽 崔月菊 李营 邓力维 杜建国
• Format: Journal Article
• Language: English
• Published: 01.08.2017
• Subjects: 各向异性; 弹性性质; 波速度; 碳酸钙; 第一原理计算; 第一性原理; 速度结构; 高压相
• ISSN: 1674-1056; 2058-3834
• DOI: 10.1088/1674-1056/26/8/089101

Elastic properties of three high pressure polymorphs of CaCO_3 are investigated based on first principles calculations.The calculations are conducted at 0 GPa–40 GPa for aragonite, 40 GPa–65 GPa for post-aragonite, and 65 GPa–150 GPa for the P2_1/c-h-CaCO_3 structure, respectively. By fitting the third-order Birch–Murnaghan equation of state（EOS）, the values of bulk modulus K_0 and pressure derivative K~＇_0 are 66.09 GPa and 4.64 for aragonite, 81.93 GPa and 4.49 for post-aragonite, and 56.55 GPa and 5.40 for P2_1/c-h-CaCO_3, respectively, which are in good agreement with previous experimental and theoretical data. Elastic constants, wave velocities, and wave velocity anisotropies of the three highpressure CaCO_3 phases are obtained. Post-aragonite exhibits 25.90%–32.10% V_P anisotropy and 74.34%–104.30% V_S splitting anisotropy, and P2_1/c-h-CaCO_3 shows 22.30%–25.40% V_Panisotropy and 42.81%–48.00% V_S splitting anisotropy in the calculated pressure range. Compared with major minerals of the lower mantle, CaCO_3 high pressure polymorphs have low isotropic wave velocity and high wave velocity anisotropies. These results are important for understanding the deep carbon cycle and seismic wave velocity structure in the lower mantle.