Dynamic Investigations of Pressure-Induced Abnormal Phase Transitions in PbTiO₃

【摘要】 The effects of pressure on phonon modes of ferroelectric tetragonal P4 mm and paraelectric cubic Pm3 m PbTiO₃are systematically investigated by using first-principles simulations.The pressure-induced tetragonal-to-cubic and subsequent cubic-to-tetragonal phase transitions are the second-order transitions,which are different from the phase transitions induced by temperature[Phys.Rev.Lett.25（1970）167].As pressure increases,the lowest A₁ and E modes of the tetragonal phase become softer and converge to the F_1u mode of the cubic phase.As pressure further increases,the lowest F_1u mode Srst hardens and then softens again,and finally diverges into A₁and E modes.The behaviors of optical phonon modes confirm the ferroelectric-to-paraelectric-to-ferroelectric phase transitions.更多还原

【Abstract】 The effects of pressure on phonon modes of ferroelectric tetragonal P4 mm and paraelectric cubic Pm3 m PbTiO₃are systematically investigated by using first-principles simulations.The pressure-induced tetragonal-to-cubic and subsequent cubic-to-tetragonal phase transitions are the second-order transitions,which are different from the phase transitions induced by temperature[Phys.Rev.Lett.25（1970）167].As pressure increases,the lowest A₁ and E modes of the tetragonal phase become softer and converge to the F_1u mode of the cubic phase.As pressure further increases,the lowest F_1u mode Srst hardens and then softens again,and finally diverges into A₁and E modes.The behaviors of optical phonon modes confirm the ferroelectric-to-paraelectric-to-ferroelectric phase transitions.更多还原