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By means of the study of the first principles within the framework of density functional theory, the inorganic metal halide perovskite CsGeX3 (X = Cl, Br, and I) is thoroughly investigated for its potential application in the field of green energy harvest. The structural, electronic, optical, mechanical, and piezoelectric properties have been calculated. Herein, the computed electronic properties reveal a direct bandgap semiconducting nature with electronic bandgap Eg$_{\text{g}}$ = 2.01, 1.38, and 0.85 eV for X = Cl, Br, and I, respectively. Since the most prominent absorption peak falls within the vis–UV region, this implies that they are the potential candidates for photovoltaic applications. To check and verify the thermal stability, the MD simulation was performed with time steps up to 5 ps. The highest piezoelectric coefficient values are 0.731, 1.829, and 12.48 C m−2 for X = Cl, Br, and I, respectively. The higher piezoelectric responses indicate the signature of the efficient energy materials for energy harvest through electromechanical processes. [ABSTRACT FROM AUTHOR]

Based on density functional theory (DFT) calculations, the electronic and magnetic properties of Co2YGe Heusler compounds (Y = Sc, Ti, V, Cr, Mn and Fe) were investigated. The density of states (DOS) and band structures were studied to understand their electronic properties. Of the investigated systems, Co2CrGe and Co2MnGe exhibited 100% spin polarisation at the EF. Co2CrGe was the most stable half-metallic ferromagnet (HMF) with a 0.24 eV energy gap at the Fermi level in the spin down channel. The total magnetic moment also increased as Y went from Sc to Fe, i.e., with increasing valence electrons. The calculated magnetic moments for Co2CrGe and Co2MnGe were 3.999 μB and 5.00 μB, respectively. Based on the calculated results, the HMF character was predicted for Co2CrGe and Co2MnGe. [ABSTRACT FROM AUTHOR]

Adsorption of carbon monoxide (CO) and hydrogen fluoride (HF) gas molecules on a ZnS monolayer with weak van der Waals interactions is studied using the DFT + U method. From our calculation, the ZnS monolayer shows chemisorption with CO ( E ads = -0.96 eV) and HF ( E ads = -0.86 eV) gas molecules. Bader charge analysis shows that charge transfer is independent of the binding environment. A higher energy barrier for CO when migrating from one optimal site to another suggests that clustering may be avoided by the introduction of multiple CO molecules upon ZnS, while the diffusion energy barrier (DEB) for HF suggests that binding may occur more easily for HF gas upon the ZnS ML. Adsorption of the considered diatomic molecule also results in a significant variation in effective mass and therefore can be used to enhance the carrier mobility of the ZnS ML. Additionally, the calculation of recovery time shows that desirable sensing and desorption performance for CO and HF gas molecules can be achieved at room temperature (300 K)., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)

Ab initio study on the family of ternary copper chalcogenides Cu 3 TaX 4 (X = S, Se, and Te) is performed to investigate the suitability of these compounds to applications as photovoltaic absorber materials. The density functional theory based full potential linearized augmented plane wave method (FP-LAPW method) is employed for computational purposes. The electronic structure and optical properties are determined including electron-electron interaction and spin-orbit coupling (SOC), within the generalized gradient approximation plus Hubbard U (GGA+ U ) and GGA+ U +SOC approximation. The large optical band gaps of Cu 3 TaS 4 and Cu 3 TaSe 4 considered ineffective for absorber materials, and also the hole effective mass has been modulated through applied pressure. These materials show extreme resistance to external pressure, and are found to be stable up to a pressure range of 10 GPa, investigated using phonon dispersion calculations. The observed optical properties and the absorption coefficients within the visible-light spectrum make these compounds promising materials for photovoltaic applications. The calculated energy and optical band gaps are consistent with the available literature and are compared with the experimental results where available., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)

Lightweight two-dimensional materials are being studied for hydrogen storage applications due to their large surface area. The characteristics of hydrogen adsorption on the h-BN bilayer under the applied electric field were investigated. The overall storage capacity of the bilayer is 6.7 wt % from our theoretical calculation with E ads of 0.223 eV/H 2 . The desorption temperature to remove the adsorbed H 2 molecules from the surface of the h-BN bilayer system in the absence of an external electric field is found to be ∼176 K. With the introduction of an external electric field, the E ads lies in the range of 0.223-0.846 eV/H 2 and the desorption temperature is from 176 to 668 K. Our results show that the external electric field enhances the average adsorption energy as well as the desorption temperature and thus makes the h-BN bilayer a promising candidate for hydrogen storage., Competing Interests: The authors declare no competing financial interest., (© 2021 The Authors. Published by American Chemical Society.)