Effect of temperature on the symmetrization of AlOOH hydrogen bonds.

• The phase transition boundary of the δ -AlOOH P2 1 nm to Pnnm structure was obtained from the bulk thermal expansion anomaly. • Hydrogen bonding symmetry points at different temperature and pressure were obtained by radial integrating the O-O distance. • The proton disorder and hydrogen bonding symmetrization phase diagrams of δ -AlOOH were constructed. Hydrogen bonding symmetrization of water-bearing minerals plays a key role in the water cycle of the deep Earth. The lower mantle is a high-temperature and high-pressure environment, and in this study a classical molecular dynamics simulation of the δ- AlOOH hydrogen bond symmetrization process is carried out using a deep learning potential model. Calculation the length of the H O bond reveals that AlOOH undergoes hydrogen bond symmetrization when the pressure reaches 9 GPa. The volume thermal expansion profile of AlOOH shows an anomalous phenomenon of negative correlation between phase transition pressure and temperature. The radial distribution functions g OH (r) and g HH (r) show the asymmetry of hydrogen bonding at 8 GPa and indicate the critical conditions for hydrogen bonding symmetry at 10 GPa. Calculations of the O 1 O 2 bond lengths show that the critical pressure required for hydrogen bond symmetry increases with temperature. Our simulation results provide some insight into the hydrogen bonding symmetry of water-bearing minerals in the deep Earth's. [ABSTRACT FROM AUTHOR]