Ultrastability and enhanced stiffness of ∼6nm TiO2 nanoanatase and eventual pressure-induced disorder on the nanometer scale

At 300 K ultrafine ∼6nm grain-size nanoanatase retains its structural integrity up to 18 GPa. There is progressive pressure-induced structural disorder to a highly disordered state at P>18GPa. Signatures of short-range order persist to well beyond 18 GPa in both the synchrotron-x-ray diffraction and Raman data. Molecular dynamics simulations suggest disorder initiated in the surface shell of a nanograin with crystallinity being retained in the core. A bulk modulus B0=237±3GPa for the nanoanatase (∼30% higher than the bulk value) is derived from the P-V data, concordant with the MD calculations.