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TiO2 : Bulk Properties and Phonons

LDA and GGA results (CASTEP) for equilibrium geometry, bulk modulus and compressibility, zero-pressure G-point phonons, and their pressure dependence. TiO2 rutile is an incipient ferroelectric.

Phase transition driven by softening of the A2u phonon with either uniaxial c axis strain or isotropic negative pressure
Ferroelectrics have many practical applications (e.g. capacitors, transducers, motors) because of their unusual physical properties.

The A2u Vibrational Mode As A Function of Strain

The calculations predict a pressure-induced ferroelectric phase transition to occur at c-axis uniaxial strain ~ 3%

Much less severe conditions than an isotropic negative pressure (Pc~ -4GPa)

Might be achievable by growing on a substrate with a lattice mismatch.

Change In Electronic Density Due to the Ferroelectric Transition

Pressure-induced instabilities in bulk TiO2 rutile
B Montanari and N M Harrison,
J. Phys. Condens. Matter 16, 273-292 (2004)

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