Phase-Transition Mechanism and the Atomic Interface Structure of Brookite to Rutile: Resolving from Machine-Learning Global Pathway Sampling

Abstract

The rich structural polymorphism of TiO2 provides an opportunity to construct a heterophase junction, which reportedly improves the photocatalyst performance. In the past, using the partial phase transition to fabricate brookite/rutile biphase materials has attracted much attention. Although many of the experiments have studied the phase transition of brookite to rutile, to date, the atomistic mechanisms and its atomic heterophase junction structure remain unclear. In this paper, the stochastic surface walking method and neural network method (SSW-NN) are utilized to map out the local potential energy surface (PES) of brookite and resolve the lowest energy barrier transition path. We show that brookite first transforms into the TiO2-II structure, and then the TiO2-II transforms into rutile with the overall orientation relation (100)B//(100)II, [010]B//[010]II, and (001)II//(101)R, [100]II//[010]R. Anatase is a byproduct rather than an intermediate phase during the brookite-to-rutile phase transition. The well-matched interfaces between brookite and TiO2-II, TiO2-II, and rutile possess spatially separated CBM and VBM, while the disordered junction between brookite and rutile shows frustrated electron/hole transport. The proposed mechanisms not only clarify the role of anatase in the brookite-to-rutile transition but also help to understand the nature of higher photocatalyst performance of the biphase.

Kinetic and Thermodynamic Transition Pathways of Silica by Machine Learning: Implication for Meteorite Impacts

“…Similar to the well-establish rutile to α-PbO 2 -type phase transition (Chen et al, 2022;Zhu et al, 2015), this transition involves layer dislocation and new chemical bonds. The intermediate structure of stishovite transition to seifertite adopts a monoclinic structure with the P2 1 /c space group (Chen et al, 2022;Müller, 1984). Simultaneously, the cell angle (γ) formed by lattice vectors b and c experience a reduction from 115°to 103°, causing a reduced interlayer distance and making it convenient for dislocation to move.…”

“…at 100 GPa. Similar to the well-establish rutile to α-PbO 2 -type phase transition (Chen et al, 2022;Zhu et al, 2015), this transition involves layer dislocation and new chemical bonds. The intermediate structure of stishovite transition to seifertite adopts a monoclinic structure with the P2 1 /c space group (Chen et al, 2022;Müller, 1984).…”

The Compound Effect of Mg and Tris(2-aminoethyl)amine for Long-Term Phase Stability in the γ-CsPbI3 Perovskite Film

“…It is previously reported that if the octahedral tilting is reduced, then the band gap is also reduced. 52,53 Therefore, the combined effect of Mg and TAEA addition leads to a reduction in the band gap and, hence, low energy shifts are observed in the PL and UV−vis absorption spectra.…”