The physical mechanisms behind the reduction of the bulk modulus of a high-pressure cubic TiO2 phase are confirmed by first-principles calculations. An unusual and abrupt change occurs in the dependence of energy on pressure at 43 GPa, indicating a pressure-induced phase transition from columbite TiO2 to a newly-identified modified fluorite TiO2 with a Pca21 symmetry. Oxygen atom displacement in Pca21 TiO2 unexpectedly reduces the bulk modulus by 34% relative to fluorite TiO2. This discovering provides a direct evidence for understanding the compressive properties of such groups of homologous materials
@article{arxiv.1004.4321,
title = {Unusual Compression Behavior of Columbite TiO2 via First-Principles Calculations},
author = {Xiang-Feng Zhou and Xiao Dong and Guang-Rui Qian and Lixin Zhang and Yonjun Tian and Hui-Tian Wang},
journal= {arXiv preprint arXiv:1004.4321},
year = {2010}
}