Uncovering the Phase Transition of Berlinite (α-AlPO4) under High Pressure: Insights from First-principles Calculations

We investigated the mechanism of crystalline-to-amorphous phase transition (CAPT) for amorphous berlinite (alpha-AlPO4) under high pressure using ab initio constant-pressure techniques. Our results show that the pressure to the change in phase transition takes place at around 20 GPa, which is inconsistent with the previous results of around 15 GPa. To confirm the feasibility of our model, the calculated X-ray powder diffraction for crystal berlinite is concordant with the standard PDF card. By assessing a full spectrum of properties including atomic structure, bonding characteristics, electron density of states and real-space pair distribution function at each pressure, we reveal the details of phase transition. Importantly, all the information from our present results elucidates that Al-O bonds play an irreplaceable role during the process of phase transition to uncover the structural and electronic properties of berlinite. Overall, our work substantiates that it is essential to utilize a wide range of changes in order to provide a comprehensive understanding on the nature of the CAPT in other inorganic oxides.