Temperature-induced amorphization in CaCO3 at high pressure: Implication for recycled CaCO3 in the transition zone

Calcite carbonate (CaCO₃) significantly affects the properties of upper mantle and plays key role in recycling deep carbon. However, its phase above 3 GPa and 1000 K is still controversial even extensive studied have been conducted. Here we reported a temperature-induced reversible aragonite-amorphization in CaCO₃ at 3.9-7.5 GPa above 1000 K. The phase boundary fall 200 K compared with Suito et al. [2001], Litasov et al. [2017], and Li et al. [2017]. Amorphous CaCO₃ shared similar structure as liquid CaCO₃ but with much larger C-O and Ca-Ca bond lengths, indicating a smaller density and a mechanism of lattice collapse for the temperature-induced amorphous phase. The lower phase transition temperature and density of amorphous CaCO₃ could aid the return of carbon from deep earth and explain the intermediate-depth earthquake.