摘要
Crystal structure predictions of Pb0.5Ba0.5 Ti03 alloys under different pressures are performed based on the parti- cle swarming optimization algorithm. The predicted stable ground-state and high-pressure phases are tetragonal ferroelectric （I4mm） and cubic para-electric （Fm3m）, respectively, whose structural details have not been re- ported. The pressure-induced colossal enhancements in piezoelectric response are associated with the mechanical and dynamical instabilities instead of polarization rotation. The band gap of the tetragonM phase is indirect and that of the cubic phase is always direct. As pressure increases, the alloy displays the similar band-gap behaviors to PbTiO3, while different from BaTiO5, which is attributed to the different orbital contributions to the valence bands. Our calculated results are in good agreement with the available data.
Crystal structure predictions of Pb0.5Ba0.5 Ti03 alloys under different pressures are performed based on the parti- cle swarming optimization algorithm. The predicted stable ground-state and high-pressure phases are tetragonal ferroelectric （I4mm） and cubic para-electric （Fm3m）, respectively, whose structural details have not been re- ported. The pressure-induced colossal enhancements in piezoelectric response are associated with the mechanical and dynamical instabilities instead of polarization rotation. The band gap of the tetragonM phase is indirect and that of the cubic phase is always direct. As pressure increases, the alloy displays the similar band-gap behaviors to PbTiO3, while different from BaTiO5, which is attributed to the different orbital contributions to the valence bands. Our calculated results are in good agreement with the available data.
基金
Supported by the Fundamental Research Funds for the Central Universities under Grant No 2013QNA38
