title: Theoretical and experimental evidence for a new post-cotunnite phase of titanium dioxide with significant optical absorption.
abstract: We report the discovery of a post-cotunnite phase of TiO2 by both density-functional ab initio calculations and high-pressure experiments. A pressure-induced phase transition to a hexagonal Fe2P-type structure (space group P62m) was predicted to occur at 161 GPa and 0 K and successfully observed by in situ synchrotron x-ray diffraction measurements at 210 GPa and 4000 K with a significant increase in opacity. This change in opacity is attributed to a reduction of band gap from 3.0 to 1.9 eV across the phase change. The Fe2P-type structure is proved to be the densest phase in major metal dioxides.
authors.affiliation: Senior Research Fellow Center, Ehime University, 2-5 Bunkyo-cho, Matsuyama, Ehime 790-8577, Japan.
authors.forename: Haruhiko
authors.initials: H
authors.lastname: Dekura
authors.forename: Taku
authors.initials: T
authors.lastname: Tsuchiya
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Kuwayama
authors.forename: Jun
authors.initials: J
authors.lastname: Tsuchiya