arXiv subjects

M. M. Woldemariam

Publications and source records attributed to M. M. Woldemariam.

3 recordsLinked to original sources

arXiv2026

Computational investigation of a perovskite LaBiO$_{3}$ for photovoltaic, thermoelectric, and optoelectronic applications

Using density functional theory (DFT) with the ONCVVPSP pseudopotential and PBE functional, this study investigates the structural, electronic, elastic, optical, and thermoelectric properties of the trigonal LaBiO$_{3}$ perovskite oxide (space group R3c). Ground-state parameters lattice constant, volume, bulk modulus, and its pressure derivative were determined using the equation of state. Applying the Hubbard correction (GGA+U) revealed an indirect, wide band gap of 3.51 eV. Mechanical properties, including the anisotropy factor, elastic modulus, and Poisson's ratio, were calculated via the Voigt-Reuss-Hill averaging scheme. The bulk-to-shear modulus ratio identifies the trigonal phase as ductile. Additionally, Debye temperatures and sound velocities were computed. Optical characteristics (absorption coefficient, refractive index, and electron energy loss function) were evaluated across a 0-35 eV spectral range. Finally, semi-classical transport coefficients, including electrical conductivity, Seebeck coefficient, and power factor, were calculated to assess the material's thermoelectric potential.

cond-mat.mtrl-sci↗

arXiv2023

Computational study of structural, elastic, electronic, phonon dispersion relation and thermodynamic properties of orthorhombic CaZrS$_3$ for optoelectronic applications

Chalcogenide perovskites offer superior thermal and aqueous stability as well as a benign elemental composition compared to organic halide perovskites for optoelectronic applications. In this study, the structural, electrical, elastic, phonon dispersion, and thermodynamic features of the orthorhombic phase of chalcogenide perovskite CaZrS$_3$ (space group Pnma) were examined by first principles calculations utilizing the plane wave pseudopotentials (PW-PPs) in generalized gradient approximations (GGA). The ground state properties such as lattice parameters, unit cell volume, bulk modulus, and its derivative were calculated and are in a good agreement with existing findings. The mechanical properties such as bulk modulus, shear modulus, Young's modulus and elastic anisotropy were calculated from the obtained elastic constants. The ratio of bulk modulus to shear modulus confirms that the orthorhombic phase of CaZrS$_3$ is a ductile material. The absence of negative frequencies in phonon dispersion curve and the phonon density of states give an indication that the structure is dynamically stable. Finally, thermodynamic parameters such as free energy, entropy, and heat capacity were calculated with variation in temperature. The estimated findings follow the same pattern as previous efforts.

cond-mat.mtrl-sci↗

arXiv2021

First principle study of structural, elastic, electronic and optical properties of Pb0.5Sn0.5TiO3 and Pb0.5Sn0.5Ti0.5(Zr0.5)O3

The structural, electronic, elastic and optical properties of tetragonal (P4mm) phase of Pb0.5Sn0.5TiO3 (PSTO) and Pb0.5Sn0.5Ti0.5(Zr0.5)O3 (PSTZO) are examined by first-principles calculations based on the density functional theory (DFT) using the pseudo-potential plane wave (PP-PW) scheme in the frame of generalized gradient approximation (GGA). We have calculated the ground state properties such as equlibrium lattice constants, volume, bulk modulus and its pressure derivative. From elastic constants, mechanical parameters such as anisotropy factor, elastic modulus and Poisson's ratio are obtained from the Voigt-Reuss-Hill average approximation. Rather than their averages, the directional dependence of elastic modulus, and Poisson's ratio are modelled and visualized in the light of the elastic properties of both systems. In addition, some novel results, such as Debye temperatures, and sound velocities are obtained. Moreover, we have presented the results of the electronic band structure, densities of states and charge densities. These results were in favourable agreement with the existing theoretical data. The optical dielectric function and energy loss spectrum of both systems are also computed. Born effective charge (BEC) of each atoms for both systems is computed from functional perturbation theory (DFPT). Finally, the spontaneous polarization is also determined from modern theory of polarization to be 0.8662 C/m2 (PSTO) and 1.0824 C/m2 (PSTZO).

cond-mat.mtrl-sci↗