Mechanism of anatase-to-columbite TiO2 phase transformation via sheared phases: first-principles calculations and high-pressure torsion experiments
arxiv(2024)
摘要
High-pressure torsion (HPT) can facilitate phase transformations in titanium
dioxide (TiO2) and stabilize its high-pressure columbite phase, as an active
photocatalyst, by shear straining under high pressure. This study aims to
understand the mechanism underlying the acceleration of the
anatase-to-columbite phase transformation by shear strain. A mechanism by
considering sheared crystal structures as intermediate phases was proposed and
examined using quantum mechanics in the framework of density functional theory
(DFT) and HPT experiments. DFT energy and phonon calculations demonstrated the
viability of the sheared structures as intermediate phases. Furthermore, the
sheared structures were observed experimentally as new metastable phases using
high-resolution transmission electron microscopy. These findings can explain
the significant effect of shear strain on pressure-induced phase transitions,
reported during severe plastic deformation of various metals and ceramics.
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