The structural origin of the unusual compression behaviors in nanostructured TiO2: insights from first-principles calculations

First-principles calculations of anatase structured TiO₂ and ZrO₂ as well as of TiO₂–B were carried up to 20 GPa in order to develop an understanding of the unusual compression and pressure-dependent phase transitions reported for nanocrystalline (nc) pure and Zr-doped anatase and nc TiO₂–B.

Unusual compression behavior of anatase TiO2 nanocrystals

The size-dependent stiffness variations in nanocrystalline anatase, a leading material for applications in photovoltaics, photocatalysis, photoelectrochromics, sensors, and optical coatings, were determined using in situ synchrotron x-ray diffraction and Raman scattering. An unusual, abrupt change in the compression curve at approximately 10 GPa and subtle breaks in the pressure shifts of the intense E(g) Raman band at approximately 10 and approximately 15 GPa have been correlated with approximately 2 A-scale disordering of nanocrystalline anatase structure that fully amorphizes under high compression.