TitleFirst-principles study of electromechanical and polar properties in perovskite oxides and half-Heusler semiconductors
NameRoy, Anindya (author), Vanderbilt, David (chair), Rabe, Karin M (internal member), Wu, Weida (internal member), Shapiro, Joel A (internal member), Zhang, Shengbai (outside member), Rutgers University, Graduate School - New Brunswick,
SubjectPhysics and Astronomy,
DescriptionThis thesis discusses electromechanical and polar properties in two well-known classes of materials, perovskite oxides and half-Heusler compounds, using first-principles calculations. Certain features of the ab initio codes, such as the capability to calculate polarization based on the modern theory of polarization, or to apply a finite electric field, are central to the problems presented in this thesis. Hence these formalisms are discussed, following a brief opening section on the basic methodology of density-functional theory. The first problem presented in this thesis concerns the nonlinear piezoelectric response of ferroelectric PbTiO₃ for the case of a polarization-enhancing electric field applied along the tetragonal axis. The dependence of the c/a ratio on electric field is found to be almost linear in the range up to 500 MV/m, contrary to what expected from Landau-Devonshire theory, but in qualitative agreement with a recent experiment. In the second problem we study the energy landscape and ferroelectric states of double perovskites of the form AA'BB'O₆ in which the atoms on both the A and B sites are arranged in rock-salt order. If a ferroelectric instability occurs, the energy landscape will tend to have minima with the polarization along tetrahedral directions, leading to a rhombohedral phase, or along Cartesian directions, leading to an orthorhombic phase. We are not aware of compounds naturally occurring in this structure, although they might be synthesized experimentally. In the final problem, we use a first-principles rational-design approach to search a large materials family, half-Heusler compounds to identify semiconductors, and then compute their piezoelectric properties. This previously-unrecognized class of piezoelectrics may benefit greatly from calculations such as those presented here. Our work may provide guidance for experimental verification of existing compounds and for the experimental realization of other potential candidates.
NoteIncludes bibliographical references
Noteby Anindya Roy
CollectionGraduate School - New Brunswick Electronic Theses and Dissertations
Organization NameRutgers, The State University of New Jersey
RightsThe author owns the copyright to this work.