Phase transition and thermodynamic properties of TiO2 from first-principles calculations

The pressure induced phase transitions of TiO₂ from anatase tocolumbite structure and from rutile to columbite structure and thetemperature induced phase transition from anatase to rutilestructure and from columbite to rutile structure are investigated byab initio plane-wave pseudopotential density functionaltheory method (DFT), together with quasi-harmonic Debye model. It isfound that the zero-temperature transition pressures from anatase tocolumbite and from rutile to columbite are 4.55 GPa and 19.92GPa,respectively. The zero-pressure transition temperatures from anataseto rutile and from columbite to rutile are 950 K and 1500 K,respectively. Our results are consistent with the availableexperimental data and other theoretical results. Moreover, thedependence of the normalized primitive cell volume V/V₀ onpressure and the dependences of thermal expansion coefficientɑ on temperature and pressure are also obtainedsuccessfully.