A theoretical investigation of the lead-free double perovskites halides Rb2 XCl6 (X = Se, Ti) for optoelectronic and thermoelectric applications.

In this study, structural, electronic, optical, thermoelectric, and thermodynamics properties of vacancy-ordered double perovskites Rb2 XCl6 (X = Se, Ti) were explored theoretically. The results revealed that Rb2SeCl6 and Rb2 TiCl6 are indirect band gap (Eg ) semiconductors with Eg values of 2.95 eV, and 2.84 eV respectively. The calculated properties (phonons, elastic constant, Poisson's ratio, and Pugh's ratio) revealed that both materials are dynamically and chemically stable and can exhibit brittle (Rb2 SeCl6 ) and ductile (Rb2 TiCl6 ) nature. From the analysis of optical parameters, it was noticed that the refractive index of the materials has a value of 1.5-2.0 where light absorption was found from the visible to the ultraviolet region. The thermoelectric properties determined by using the BoltzTrap code demonstrated that at room temperature, the Figure of merit (ZT) was found to be 0.74 and 0.76 for Rb2 SeCl6 and Rb2 TiCl6 , respectively. Despite a moderate value of ZT in such materials, further studies might explore effective methods for tuning the electronic band gap and improving the thermoelectric response of the material for practical energy production applications.

Ameliorating the Mechanical Parameters, Thermal Stability, and Wettability of Acrylic Polymer by Cement Filling for High-Efficiency Waterproofing.

Acrylic polymer/cement nanocomposites in dark and light colors have been developed for coating floors and swimming pools. This work aims to emphasize the effect of cement filling on the mechanical parameters, thermal stability, and wettability of acrylic polymer. The preparation was carried out using the casting method from acrylic polymer coating solution, which was added to cement nanoparticles (65 nm) with weight concentrations of (0, 1, 2, 4, and 8 wt%) to achieve high-quality specifications and good adhesion. Maximum impact strength and Hardness shore A were observed at cement ratios of 2 wt% and 4 wt%, respectively. Changing the filling ratio has a significant effect on the strain of the nanocomposites. The contact angle was increased as the concentration of additives and cement increased, indicating that the synthesized coating is not hydrophilic and does not allow water permeability through it. The results show that the acrylic polymer/cement with a cement ratio of 8 wt% is the best nanocomposite for high-efficiency waterproofing.

Adsorption of CO over the Heusler alloy CrCoIrGa(001) surface: first-principles insights.

In this study, the adsorption of CO molecule over (001) surface of the Heusler alloy CrCoIrGa, has been investigated using DFT+U calculations. It is demonstrated that, after relaxation, the (001) surface retains the bulk atomic positions, exhibiting no apparent surface reconstruction. Owing to the emergence of unsaturated bonds at the surface, the surface layer atoms are found to carry more spin-polarization (SP) and atomic moments than that of inner layer atoms. The ground state total SP (magnetic moment) is found to be 27% (42.256 µ B). To explore the CO adsorption over the surface, five different adsorption configurations (sites) are considered and the strength of CO to surface interaction is estimated from the computed density of states (DOS), adsorption energy (E a), change in magnetic moment (ΔM), vertical height between molecule and surface (h), charge transfer (ΔQ), and charge density difference (CDD) plots. For all configurations, the E a lies in the range of -2.15 to -2.34 eV, with CO molecule adsorbed on the top of Ir atom as the most favorable adsorption configuration. The observed E a, ΔQ, h, and ΔM values, collectively predict that the (001) surface has strong interaction (chemisorption) with CO gas molecule, thus, might be useful in gas sensing applications.