Structural, elastic, electronic, and optical properties of cubic perovskite CsCaCl3 are calculated using the full-potential linearized augmented plane wave method in the density functional theory. The exchange-correlation potential is evaluated using the local density approximation and generalized gradient approximation. Further, the modied BeckeJohnson potential is also applied for studying the electronic and optical properties. The calculated structural properties such as equilibrium lattice constant, the bulk modulus and its pressure derivative are in good agreement with the available data. The elastic properties such as elastic constants, anisotropy factor, shear modulus, Young's modulus and Poisson's ratio are calculated. The calculations of electronic band structure, density of states and charge density show that this compound has an indirect energy band gap (M Γ) with a mixed ionic and covalent bonding. Calculations of the optical spectra such as the real and imaginary parts of dielectric function, optical reectivity, absorption coecient, optical conductivity, refractive index, extinction coecient and electron energy loss are performed for the energy range of 030 eV. Most of the studied properties are reported for the rst time for CsCaCl3.

Electronic, structural and optical properties of the cubic perovskite CsCaF3 are calculated by using the full potential linearized augmented plane wave (FP-LAPW) plus local orbitals method with generalized gradient approximation (GGA) in the framework of the density functional theory. The calculated lattice constant is in good agreement with the experimental result. The electronic band structure shows that the fundamental band gap is wide and indirect at (Γ -𝑅) point. The contribution of the different bands is analyzed from the total and partial density of states curves. The charge density plots show strong ionic bonding in Cs-F, and ionic and weak covalent bonding between Ca and F. Calculations of the optical spectra, viz., the dielectric function, optical reflectivity, absorption coefficient, real part of optical conductivity, refractive index, extinction coefficient and electron energy loss, are performed for the energy range 0-30 eV.

Lithium-lanthanum titanate, Li 0•29 La 0•57 TiO 3 , is prepared by solid-state reaction method and it is furnace-cooled to room temperature. X-ray diffraction results indicated that the compound has tetragonal perovskite-like structure and the lattice parameters are determined as a = 3•8714 Å and c = 7•7370 Å. The average grain size is found to be 5 μm from SEM micrograph. The analysis of FTIR and Raman spectra of the sample supported tetragonal structure inferred from XRD data. The impedance spectrum of the sample is separated into bulk and grain boundary parts by analysing the impedance data. The high bulk ionic conductivity is reported as 1•12 × 10 −3 S cm −1 at room temperature. D.C. conductivity measurements indicate that the compound is a good ionic conductor.

The first principles calculation within the full potential linearized augmented plane wave (FP-LAPW) method is applied to study the structural, electronic and elastic properties of cubic perovskite-type compounds KCaF 3 and RbCaF 3 . The exchange correlation effects are included through the LDA, GGA and modified Becke-Johnson (mBJ) exchange potential. The calculated structural properties such as equilibrium lattice constant, the bulk modulus and its pressure derivative are in good agreement with the available data. KCaF 3 and RbCaF 3 have wide and indirect band gaps and they agree with experimental values. The elastic properties such as elastic constants, anisotropy factor, shear modulus, Young's modulus and Poisson's ratio are obtained for the first time. KCaF 3 and RbCaF 3 are elastically anisotropic and the B/G ratio indicate that these are ductile materials.

No abstract