High-pressure polymorphs of ZnCO₃: evolutionary crystal structure prediction

Area of Science:

• Materials Science
• Solid-State Chemistry
• High-Pressure Physics

Background:

• Zinc carbonate (ZnCO3) exhibits complex structural behavior under extreme pressure.
• Understanding these transformations is crucial for materials science and geochemistry.

Purpose of the Study:

• To investigate the high-pressure phase transitions of zinc carbonate (ZnCO3).
• To predict and analyze the stable structures of ZnCO3 at various pressures.

Main Methods:

• Utilized the universal structure prediction method.
• Employed density functional theory (DFT) calculations.
• Performed separate high-pressure calculations with varying formula units per unit cell.

Main Results:

• Identified two pressure-induced phase transitions at 78 GPa and 121 GPa.
• Determined the most stable structures: R-3c (ambient), C2/m (78-121 GPa), and P2(1)2(1)2(1) (>121 GPa).
• Observed the formation of new zinc-oxygen bonds at 78 GPa, correlating with the first phase transition.

Conclusions:

• The predicted phase transitions and structures for ZnCO3 under pressure are consistent with experimental data.
• The formation of new Zn-O bonds is a key factor driving the high-pressure phase transitions in ZnCO3.
• Mechanical properties of the ambient R-3c phase were calculated and validated against existing data.