arXiv subjects

H. Akter

Publications and source records attributed to H. Akter.

3 recordsLinked to original sources

arXiv2023

Oxysulfide Perovskites: Reduction of the Electronic Band Gap of RbTaO3 by Sulfur Substitution to Enhance Prospective Solar Cell and Thermoelectric Performances

In this study, the effects of sulfur substitution on the structural, mechanical, electronic, optical, and thermodynamic properties of RbTaO3-xSx have been investigated using the WIEN2k code in the framework of density functional theory (DFT). The cubic phase of RbTaO3 transforms to tetragonal for RbTaO2S and RbTaOS2, the later transforms again to a cubic phase with added sulfur for RbTaS3. The results showed that substituting S for O anions in RbTaO3 effectively decreased the band gap from 2.717 eV to 1.438 eV, 0.286 eV, and 0.103 eV for the RbTaO3,RbTaO2S, RbTaOS2, and RbTaS3 compounds, respectively. The optical constants such as dielectric constants, refractive index, absorption coefficient, photoconductivity, reflectivity and loss function have been calculated and analyzed. The elastic constants and moduli, and their anisotropic nature were also investigated. Finally, the Debye temperature, thermal conductivity, melting temperature, specific capacities and thermal expansion coefficients were computed and analyzed using established formalisms. The reduced band gap (1.438 eV) and high absorption coefficient (~106 cm-1) of RbTaO2S makes it suitable for solar cell applications and for other visible light devices. Reduction of the band gap and phonon thermal conductivity owing to Ssubstitution is expected to enhance thermoelectric performances of the S-containing phases

cond-mat.mtrl-sci↗

arXiv2023

DFT insights into MAX phase borides Hf2AB [A = S, Se, Te] in comparison with MAX phase carbides Hf2AC [A = S, Se, Te]

In this work, density functional theory (DFT) based calculations were performed to compute the physical properties (structural stability, mechanical behavior, electronic, thermodynamic, and optical properties) of synthesized MAX phases Hf2SB, Hf2SC, Hf2SeB, Hf2SeC, Hf2TeB, and the as-yet-undiscovered MAX carbide phase Hf2TeC. Calculations of formation energy, phonon dispersion curves, and elastic constants confirmed the stability of the aforementioned compounds. The obtained values of lattice parameters, elastic constants, and elastic moduli of Hf2SB, Hf2SC, Hf2SeB, Hf2SeC, and Hf2TeB showed fair agreement with earlier studies, whereas the values of the mentioned parameters for the predicted Hf2TeC exhibit a good consequence of B replacement by C. The anisotropic mechanical properties are exhibited by the considered MAX phases. The metallic nature and its anisotropic behavior were revealed by the electronic band structure and density of states. The analysis of the thermal properties Debye temperature, melting temperature, minimum thermal conductivity, and Gruneisen parameter confirmed that the carbide phases were more suited than the boride phases considered herein. The MAX phase response to incoming photons further demonstrated that they were metallic. Their suitability for use as coating materials to prevent solar heating was demonstrated by the reflectivity spectra. Additionally, this study demonstrated the impact of B replacing C in the MAX phases.

cond-mat.mtrl-sci↗

arXiv2021

Digital competency of educators in the virtual learning environment: a structural equation modeling analysis

This study integrates the educators digital competency (DC), as an individual characteristic construct of the task-technology fit (TTF) theory, to examine a better fit between Moodle using and teaching task, and to investigate its effect on both Moodles utilization and their task performance. For assessing our proposed hypotheses, an online survey was conducted with 238 teaching staff from different departments of universities in Malaysia. Using Structural Equation Modelling (SEM), our analysis revealed that all the proposed components (i.e., technology literacy, knowledge deepening, presentation skills, and professional skills) of digital competency significantly influenced the TTF. The Task-Technology Fit was also found as an influential construct, which positively and significantly affected both Moodles utilization and teachers task performance. Besides, Moodles utilization was confirmed to be a substantial determinant of the performance impact. In the end, this study included limitations and future directions based on how the study's contribution can support academics and practitioners for assessing and understanding what particular components of digital competency impact TTF, which in turn may influence the systems utilization and performance impact.

cs.HC↗