Solidification process of ABO3-type perovskites: Kinetic two-phase growth method with optimized potential

Abstract

The functional properties of ABO3-type perovskite materials have garnered extensive attention, yet their solidification properties have remained challenging to investigate due to high-temperature environments and characterization limitations. In this study, molecular dynamics simulations are employed to comprehensively explore the melting, quenching, and crystal growth processes of SrTiO3 (STO) structural evolution. Through iterative fitting and optimization of ion effective charge, a set of potential functions capable of accurately simulating the high-temperature melting of STO are derived. The melting point obtained for STO (2403 K) using the two-phase coexistence method closely corresponds to the empirical value (2333 K), affirming the precision of the optimized potential. Quenching the molten STO yields an amorphous structure characterized primarily by Ti-O six-fold coordination, which increased by 13.09% when reduced to 300 K at a cooling rate of 0.1 K/ps. Notably, the results for different cooling rates revealed that slower cooling rates and lower temperatures yielded more ordered amorphous structures. To circumvent the formation of amorphous states during crystal growth of perovskite materials, we have developed a kinetic two-phase growth (KTPG) method. This approach regulates the cooling rate within a solid-liquid two-phase system, maintaining constant low supercooling at the interface to mimic STO crystal growth kinetics. Cooling at 0.01 K/ps to 1760 K leads to a notable transformation, with the percentage of Ti-O six-fold coordination reaching 90%. This signifies substantial progress in achieving crystal growth through this method, highlighting its efficacy in facilitating crystal formation from the melt phase.