Electronic structure, optical and dielectric properties of BaTiO₃/CaTiO₃/SrTiO₃ ferroelectric superlattices from first-principles calculations

Abstract

The electronic structure, lattice vibrations, optical, dielectric and thermodynamic properties of BaTiO3/CaTiO3/SrTiO3 (BT/CT/ST) ferroelectric superlattices are calculated by using first-principles. The lattice parameters after relaxation are in good agreement with the experimental and other theoretical values within error of 1%. The band structure shows an indirect band gap with the value of about 2.039eV, and a direct band gap of 2.39eV at the Г point. The density of states and the electron charge density along [001] axis are calculated and show the displacement of Ti ions along the [001] axis. The strong hybridization between O 2p and Ti 3d contributes to the ferroelectricity of BT/CT/ST ferroelectric superlattices. The Γ modes are stable, while the vibration modes at A, M, R, and X point are unstable governing the nature of phase transition. The static dielectric tensor including the ionic contribution is calculated and the permittivity parallel to the optical axis is almost eight times more than the permittivity vertical the axis, exhibiting the strong anisotropy. The thermodynamic enthalpy, free energy, entropy, and heat capacity are also investigated based on the phonon properties.

First-principles study on the electronic, optical, and transport properties of monolayer α - and β -GeSe

“…where P denotes the principle value. The absorption coefficient α(ω) and reflectivity R(ω) can be subsequently given by [36][37][38]…”

First‐principle calculations of optical properties of monolayer arsenene and antimonene allotropes

“…Based on the dielectric function of α− and β−As/Sb, the optical properties including the energy loss spectrum L(ω) can be subsequently given by [31][32][33] For the dielectric function (ω) of α−As/Sb shown in Fig. 6(a) and (b) respectively, strong inplane anisotropy ( aa bb ) is observed, which is attributed to the anisotropic crystal structure of α−As/Sb.…”

Chemical composition and temperature dependence of the energy storage properties of Ba1‐xSrxTiO3 ferroelectrics

“…Pure SrTiO 3 should not have a ferroelectric‐paraelectric phase transition due to its quantum paraelectricity. SrTiO 3 can remain paraelectric until the temperature is < 0.3 K, but ferroelectric polarization can easily occur if the balance of forces is broken by slight perturbations in the lattice structure, such as doping, strain and oxygen isotope substitution . Experimentally, at a low temperature, each oxygen octahedron with a Ti ion in the center of SrTiO 3 exhibits a small rotational shift with respect to the structural frame of the Sr ions, and the magnitude of the angle has been reported to be 1.6° at 77 K. This results in an antiferrodistortive I4/mcm structure .…”