Structural transitions of calcium carbonate by molecular dynamics simulation.

This article focuses on the investigation of structural phase transitions of calcium carbonate (CaCO₃) under varying temperature and pressure conditions using molecular dynamics (MD) simulations with the Raiteri potential model. The study reproduces known temperature-driven transitions from calcite to CaCO₃-IV and then to CaCO₃-V at 1 bar, characterizing the CaCO₃-IV to CaCO₃-V transition as continuous (potentially second order), and identifies a higher-temperature transition to a more disordered phase. Under constant temperature (1600 K), pressure-driven transitions from CaCO₃-V to CaCO₃-IV at ~2 GPa and from CaCO₃-IV to CaCO₃-Vb at ~4.25 GPa are observed, with the latter classified as a first-order phase transition. The CaCO₃-Vb phase is suggested as a possible intermediate structure between calcite and post-aragonite in the B1 to B2 cation array transition. The simulations qualitatively align with experimental findings but do not capture the transition to aragonite, likely due to timescale and modeling limitations. The study also notes size effects related to defect formation and highlights the need for further research on domain and defect mechanisms in CaCO₃ phase transitions.