Electronic band structure, thermodynamics and optical characteristics of BeO1−A (A = S, Se, Te) alloys: Insights from ab initio study

A holistic approach to understanding structural, magneto-electronic, thermoelectric, and thermodynamic properties of RhMnZ (Z = Si, Ge) half Heusler alloys

This study thoroughly examines the structural, mechanical, thermal, electronic, optical, and thermoelectric properties of RhMnZ (Z = Si, Ge) half-Heusler compounds, which feature 18 valence electrons. Using density functional theory (DFT) within the WIEN2k computational framework, the ground-state properties of these compounds were determined to establish a foundational understanding of their physical characteristics. To further assess their thermoelectric potential, the Boltzmann transport equation was applied with the constant relaxation time approximation, allowing for precise calculations of thermal and electrical conductivity. Results indicate that the lattice constants of RhMnSi and RhMnGe span from 5.6394 Å to 5.7447 Å, highlighting consistent crystalline structures that lack band gaps, confirming their metallic nature. Detailed elastic and thermodynamic evaluations demonstrate that these compounds are mechanically stable, displaying ductile and anisotropic behavior. The study further reveals that thermal properties, including specific heat and entropy, tend to increase with the atomic number of Z, suggesting that RhMnGe may have a slightly higher heat capacity compared to RhMnSi. For thermal conductivity estimation, Slack's model was employed, indicating that these compounds possess high lattice thermal conductivity-a crucial factor for thermoelectric materials. The substantial figure of merit (ZT) observed in these compounds, especially at elevated temperatures, points to their potential efficiency in thermoelectric applications. The combination of high thermal conductivity, favorable mechanical stability, and robust thermoelectric properties identifies RhMnZ compounds as promising candidates for use in energy conversion technologies, particularly where efficient heat-to-electricity conversion is needed. This study thus lays the groundwork for future applications of RhMnSi and RhMnGe in thermoelectric devices.

Investigation of the electronic and optical properties of bilayer CdS as a gas sensor: first-principles calculations

We utilised first-principles computations based on density functional theory to investigate the optical and electronic properties of bilayer CdS before and after the adsorption of gas molecules. Initially, we examined four candidate adsorption sites to determine the best site for adsorbing CO, CO2, SO2, H2S, and SO. In order to achieve the optimal adsorption configurations, we analysed the adsorption energy, distance, and total charge. Our findings reveal that the CdS bilayer forms a unique connection between the O and Cd atoms, as well as the S and Cd atoms, which renders it sensitive to SO2, H2S, and SO through chemical adsorption, and CO and CO2 through strong physical adsorption. The adsorption of gas molecules enhances the optical properties of the CdS bilayer. Consequently, the CdS bilayer proves to be a highly efficient gas sensor for SO2, H2S, and SO gases.

Semiconducting Chalcogenide Alloys Based on the (Ge, Sn, Pb) (S, Se, Te) Formula with Outstanding Properties: A First-Principles Calculation Study

Very recently, a new class of the multicationic and -anionic entropy-stabilized chalcogenide alloys based on the (Ge, Sn, Pb) (S, Se, Te) formula has been successfully fabricated and characterized experimentally [Zihao Deng et al., Chem. Mater. 32, 6070 (2020)]. Motivated by the recent experiment, herein, we perform density functional theory-based first-principles calculations in order to investigate the structural, mechanical, electronic, optical, and thermoelectric properties. The calculations of the cohesive energy and elasticity parameters indicate that the alloy is stable. Also, the mechanical study shows that the alloy has a brittle nature. The GeSnPbSSeTe alloy is a semiconductor with a direct band gap of 0.4 eV (0.3 eV using spin-orbit coupling effect). The optical analysis illustrates that the first peak of Im(ε) for the GeSnPbSSeTe alloy along all polarization directions is located in the visible range of the spectrum which renders it a promising material for applications in optical and electronic devices. Interestingly, we find an optically anisotropic character of this system which is highly desirable for the design of polarization-sensitive photodetectors. We have accurately predicted the thermoelectric coefficients and have calculated a large power factor value of 3.7 × 10¹¹ W m^-1 K^-2 s^-1 for p-type. The high p-type power factor is originated from the multiple valleys near the valence band maxima. The anisotropic results of the optical and transport properties are related to the specific tetragonal alloy unit cell.

Theoretical analysis of the structural and electronic properties of the interaction of boron nitride diamantane nanocrystal with the drug hydroxyurea as an anticancer drug

The density functional theory calculations with hybrid B3LYP/6-31G(d,p) basis sets have been used to examine the structural and electronic properties of boron nitride (BN) diamantane interacted with the drug hydroxyurea (HU) as an anticancer drug. The findings have been shown that there is a decrease in the total energy after combining the drug with diamantane. The energy levels of HOMO and LUMO analyses indicate that the value of HOMO energy increased slightly, while the value of LUMO energy decreased significantly in these systems in the HU/BN diamantane. In addition, the decreasing of the energy gap between HOMO and LUMO confirms a strong bond between the drug hydroxyurea and BN diamantane. Finally, the drug's stability and reactivity with BN diamantane were investigated by measuring chemical reaction characteristics such as chemical potential, electron affinity, global hardness, and electrophilicity index. As a result, the nanocrystal of BN diamantane can be considered a vector for the delivery of anticancer drugs within biological systems.

First-principles investigation of nonmetal doped single-layer BiOBr as a potential photocatalyst with a low recombination rate

Nonmetal doping is an effective approach to modify the electronic band structure and enhance the photocatalytic performance of bismuth oxyhalides.

Unraveling the effect of Gd doping on the structural, optical, and magnetic properties of ZnO based diluted magnetic semiconductor nanorods

The structural, magnetic, and optical properties of the pristine and Gd-doped ZnO nanorods (NRs), prepared by facile thermal decomposition, have been studied using a combination of experimental and density functional theory (DFT) with Hubbard U correction approaches. The XRD patterns demonstrate the single-phase wurtzite structure of the pristine and doped ZnO. The rod-like shape of the nanoparticles has been examined by FESEM and TEM techniques. Elemental compositions of the pure and doped samples were identified by EDX measurement. Due to the Burstein–Moss shift, the optical band gaps of the doped samples have been widened compared to pristine ZnO. The PL spectra show the presence of complex defects. Room temperature magnetic properties have been measured using VSM and revealed the coexistence of paramagnetic and weak ferromagnetic ordering in Gd³⁺ doped ZnO-NRs. The magnetic moment was increased upon addition of more Gd ions into the ZnO host lattice. The DFT+U calculations confirm that the presence of vacancy-complexes has a significant effect on the structural, electronic, and magnetic properties of a pristine ZnO system.

Gd doped ZnO nanorods.