Theoretical Investigation of Crystal and Electronic Structure of piezoelectric AgNb0.5Ta0.5O3

Singh, Shivani and Niranjan, Manish K (2015) Theoretical Investigation of Crystal and Electronic Structure of piezoelectric AgNb0.5Ta0.5O3. Masters thesis, Indian Institute of Technology Hyderabad.

Preview

Text
PH-13M1013.pdf - Published Version
Download (1MB) | Preview

Abstract

We present an ab-initio study of structural and electronic properties of lead-free oxide AgNb0.5Ta0.5O3 (ANTO) in orthorhombic Pbcm space group and monoclinic p2/m space group. In our calculations, both the symmetries (orthorhombic Pbcm and monoclinic p2/m) of AgNb0.5Ta0.5O3 show small relative energy difference ( ~ 0.6062 eV), thus suggesting the coexistence of both the unit cells at the room temperature. Band Structure of ANTO infers that the compound is an insulator or semiconductor with direct band gap. Conduction band of ANTO, consists of Nb-4d and Ta-5d and upper level of valence band is contributed by Ag-4d and O-2p while lower level is contributed by Nb-4d and Ta-5d along with O-2p. Charge density of ANTO is uniformly spherical around Ag deducing an ionic bond between Ag-O and non uniform spherical charge density around Ta/Nb-O suggests an ionic covalent bond due to high electronegativity of O. Large phonon frequency belongs to O atom and the phonon frequency ranging in lower frequency range corresponds to Ag-O and Nb-o/Ta-O vibrations, respectively.

[error in script]

IITH Creators: