The mechanism of high pressure-induced phase transition in titanium dioxide: <i>ab initio</i> molecular dynamics simulations

The phase transition behavior of anatase TiO₂ nanocrystals under high pressure has attracted considerable attention; however, systematic understanding of the atomic-scale mechanism of the solid-solid phase transition remains unclear. Therefore, in the current work, TiO₂ supercells of different sizes were constructed and the atomic rearrangement processes were investigated through <i>ab initio</i> molecular dynamics (AIMD) simulations. Under high pressure, TiO₂ undergoes a structural phase transition from the anatase phase to the baddeleyite phase, accompanied by the coordination polyhedron transformation from [TiO₆] octahedra to [TiO₇] mono-capped trigonal prisms, following a non-diffusive transition pathway. The simulations reveal distinct structural transformation behaviors: the larger supercell exhibits a layer-by-layer transition with a reduced energy barrier (0.26 eV) compared to the smaller one. These findings contribute to the mechanistic understanding of structural phase transformations in TiO₂ and provide insights into the rational design of pressure-sensitive crystalline materials.