Abstract
The structural, electronic, and elastic properties of tetragonal phase of SnTiO3 and PbTiO3 are investigated using first principle calculations. The unknown exchange-correlation functional is approximated with generalized gradient approximation (GGA) as implemented in pseudopotential plane wave approach. The convergence test of total energy with respect to energy cutoff and k-point sampling is preformed to ensure the accuracy of the calculations. The structural properties such as equilibrium lattice constant, equilibrium unit cell volume, bulk modulus, and its derivative are in reasonable agreement with the previous experimental and theoretical works. From elastic constants, mechanical parameters such as anisotropy factor A, shear modulus G, bulk modulus B, Young’s modulus E, and Poison’s ratio n are determined by using Voigt–Reuss–Hill average approximation. In addition, Debye temperature and longitudinal and transversal sound velocities are predicted from elastic constants. The electronic band structure and density of states of both compounds are obtained and compared with the available experimental as well as theoretical data. Born effective charge (BEC), phonon dispersion curve, and density of states are computed from functional perturbation theory (DFPT). Lastly, the spontaneous polarization is determined from the modern theory of polarization, and they are in agreement with the previous findings.
Highlights
ABO3 perovskites are important for a variety of high technology applications as a result of their diverse physical properties [1]
generalized gradient approximation (GGA)-PBE [13] is used in this study to approximate the exchange-correlation functional as we have no pseudopotential generator for hybrid functional in Quantum ESPRESSO package currently. e k-point sampling of the Brillion zone is constructed using Monk Horst Pack Mesh scheme [14] with 6 × 6 × 6 grids in primitive cells of compounds. e Born effective charges, optical dielectric constants, and phonon dispersion curve of the ferroelectric materials are calculated from density functional perturbation theory (DFPT) using local density approximation (LDA)
To optimize the structural parameters of SnTiO3 and PbTiO3, 80 Ry cutoff energy and 6 × 6 × 6 k-point grid size is used from our convergence test
Summary
ABO3 perovskites are important for a variety of high technology applications as a result of their diverse physical properties [1]. Due to its high spontaneous polarization and wide temperature stability of ferroelectric phase, the compound has got a strong interest. PbTiO3 compound has a tetragonal phase (space group P4mm) with ferroelectric property, while for the temperature above. In spite of great physical importance, the most widely used ferroelectric ceramics based on the PbTiO3 and PbZrO3 solid solution are generically called PZT. Most of the theoretical reports with regard to the SnTiO3 materials are merely focused on their physical properties and high polarization effect in the ferroelectric phase [10]. The elastic properties, Poison’s ratio, anisotropic index, Debye temperature, born effective charge, phonon dispersion, and spontaneous polarization of tetragonal phase of SnTiO3 which is, expected to replace PbTiO3 is, not well studied and needs more investigation. To predict a specific device application and improvements, a deeper and fundamental understanding of the properties of the ferroelectric material are necessary. erefore, studying the structural, elastic, lattice dynamics, and electronic properties as well as understanding the overall characteristics of the system is utmost important
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