Phase transition trend of calcite on the molecular scale

Abstract

Polymorph predication was used to investigate the intermediate structures during the thermal decomposition processing of calcite. It found that rhombohedral () calcite should directly transform to the chiral orthorhombic structure (Pna21) and it is less likely to undergo phase transition from the monoclinic structure (Cc) to monoclinic structure (P21). The monoclinic structure (C2) of IMC1 and the monoclinic structure (P212121) of IMD1 may be a metastable calcium carbonate at very high pressure, respectively. The transformation results have been compared with experiment and calculation to a certain extent. The result also shows that the volume expansion of the intermediate structures (Pna21) is anisotropic. The a-axis length increases slightly, the b-axis length increases remarkably, and the c-axis length decreases rapidly. Because calcite is thermodynamically the most stable carbonate mineral, it can provide valuable information to study the thermal decomposition mechanism of metal carbonates and design new functional materials.