Phase diagram and physical properties anisotropy of strontianite

Abstract

The physical properties and anisotropy of carbonates at high pressure are fundamental to understanding the deep carbon cycle and storage. Here, we redraw the phase diagram of strontianite (SrCO3) by first-principles calculations combined with lattice dynamics and study its physical properties and anisotropy at high pressure. The results show that there are only Pnma and Pmmn phases in SrCO3 in the entire Earth's mantle, and there is no R3m phase. The SrCO3 polymorphs have a large elastic anisotropy. SrCO3 polymorphs are a kind of carbonate with high density, low wave velocity, and low wave velocity anisotropy. The linear thermal expansion coefficient of SrCO3-Pmmn was obtained for the first time by using the linear elastic compression coefficient combined with the volume thermal expansion coefficient. The results are of great significance for understanding the high-pressure behavior of Sr-carbonates.