A first principles study of corundum V2O3 material as a promising anode for Li/Mg/Al-ion batteries.

Rechargeable multivalent metal-ion batteries have attracted the attention of researchers, owing to their great potential to meet the future demands from portable devices to large-scale energy storage. This is mainly due to their natural abundance, high safety levels, and high energy density. In this work, we study the thermodynamic, electronic, and structural properties, and the variation in the open-circuit voltage during the insertion of Li, Mg and Al atoms into corundum V2O3 using first principles calculations. The formation energies of fully lithiated LiV2O3, magnesiated Mg0.5V2O3, and aluminiated Al0.5V2O3 systems are all negative, indicating the possibility of introducing Li/Mg/Al atoms into V2O3 spontaneously. Furthermore, we have shown that the open circuit voltage of Li+ starts with a value of 2.04 V, which is in good agreement with the experimental results. On the other hand, it takes a lower value equal to 0.31 and 0.41 V for Mg2+ and Al3+ respectively, which is required for negative electrode materials. The maximum theoretical capacity of V2O3 is 1072 mA h g-1 for magnesium-ion batteries (MIBs) and 1679 mA h g-1 for aluminum-ion batteries (AIBs). Based on these calculated properties, we can propose corundum V2O3 as a promising negative electrode for Mg/Al-ion batteries.

Optimal allocation strategies for prioritized geographical vaccination for Covid-19.

While SARS-CoV-2 vaccine distribution campaigns are underway across the world communities, these efforts face the challenge of effective distribution of limited supplies. We wonder whether suitable spatial allocation strategies might significantly improve a campaignfls efficacy in averting damaging outcomes. In the context of a limited and intermittent COVID-19 supply, we investigate spatial prioritization strategies based on six metrics using the SLIR compartmental epidemic model. We found that the strategy based on the prevalence of susceptible individuals is optimal especially in early interventions and for intermediate values of vaccination rate. It minimizes the cumulative incidence and consequently averts most infections. Our results suggest also that a better performance is obtained if the single batch allocation is supplemented with one or more updating of the priority list. Moreover, the splitting of supply in two or more batches may significantly improve the optimality of the operation.

Revealing the impact of strontium doping on the optical, electronic and electrical properties of nanostructured 2H-CuFeO2 delafossite thin films.

Delafossite materials are considered to be a promising range of transparent conductive oxides for optoelectronic applications. The complications that have held back their implementation in practical devices lie in the complex growth methods that are required and in the formation of undesirable secondary phases. Herein, a fast, simple, and low-cost deposition method allowing the deposition of high-quality 2H-CuFeO2 nanostructured thin films is employed. The effect of Sr doping on the properties of spray-coated CuFeO2 thin film annealed at 850 °C is reported. X-ray diffraction (XRD) analysis revealed the delafossite structures of all the samples corresponding to the 2H-CuFeO2 phase. The lattice spacing decreased with increasing substitution of Sr at the Cu site. Raman analysis further authenticated the structural results collected via XRD analysis. Surface scanning using field-emission scanning electron microscopy revealed the formation of nanostructured CuFeO2 thin film possessing high crystalline quality, with the nanocrystal size increasing as the dopant content was increased. Energy-dispersive X-ray analysis allowed the quantification of the elements content via determining the ratios of the main elements as well as the dopant content in each sample. The optical properties of the samples showed strong light absorption in the visible region with a decrease in the band gap values with Sr insertion. First-principles calculations using density functional theory (DFT) were conducted to strengthen the experimental findings regarding the nature of the bonds in the hexagonal lattice of the CuFeO2 compound and the effect of Sr doping on its characteristics. The electrical properties measured at room temperature revealed p-type conductivity with tunable resistivity, while the samples displayed increased electron mobility as a function of the dopant content. Consequently, our work introduced an efficient and cost-effective synthesis route for the preparation of high-quality nanostructured 2H-CuFeO2 thin films, paving the way to facilitate further device applications.

Unraveling the microstructural and optoelectronic properties of solution-processed Pr-doped SrSnO3 perovskite oxide thin films.

The inorganic stannous-based perovskite oxide SrSnO3 has been utilized in various optoelectronic applications. Facilitating the synthesis process and engineering its properties, however, are still considered challenging due to several aspects. This paper reports on a thorough investigation of the influence of rare-earth (praseodymium) doping on the microstructural and optoelectronic properties of pure and Pr-doped SrSnO3 perovskite oxide thin films synthesized by a two-step simple chemical solution deposition route. Structural analysis indicated the high quality of the obtained phase and the alteration generated from the insertion of impurities. Surface scanning illustrated the formation of homogenous and crack-free SrSnO3 thin films with a nanorod morphology, with an augmentation in size as the dopant ratios increased. Optical properties analysis showed an enhancement in the samples optical absorption with wide-range bandgap tuning. First-principles calculations revealed the exchange interactions between the 3d-4f states and their impact on the electronic properties of the pristine material. Hall-effect measurements revealed an immense decrement in the resistivity of the films upon increment of doping ratios, passing from 7.3 × 10-2 Ω cm for the undoped sample to 4.8 × 10-2 Ω cm for 7% Pr content, while a reverse trend was observed on the carrier mobility, rising from 2.5 to 7.6 cm2 V-1 s-1 for 7% Pr content. The results emphasized the efficiency of the simple synthesis route to produce high-quality samples. The current findings will contribute to paving the way towards expanding the utilization of simple and cost-effective chemical solution deposition methods for the fast and large area growth of stannous-based perovskite oxides for optoelectronic applications.

Higher Conductivity and Enhanced Optoelectronic Properties of Chemically Grown Nd-Doped CaSnO3 Perovskite Oxide Thin Films.

Stannous-based perovskite oxide materials are regarded as an important class of transparent conductive oxides for various fields of application. Enhancing the properties of such materials and facilitating the synthesis process are considered major challenging aspects for proper device applications. In the present paper, a comprehensive and detailed study of the properties of spray-coated CaSnO3 thin films onto the Si(100) substrate is reported. In addition, the substrate effect and the incorporation of rare-earth Nd3+ on engineering the characteristics of CaSnO3 thin films annealed at 800 °C are included. X-ray diffraction (XRD) analysis results revealed the orthorhombic structure of all the samples with an expansion of lattice spacing as the substitution of Nd at the Ca site increased. The Raman and FT-IR analysis further confirmed the structural results collected via the XRD analysis. Surface scanning using field-emission scanning electron microscopy revealed the formation of quasi-orthorhombic CaSnO3 grains with an increase in size as dopant content increased. Energy-dispersive X-ray analysis allowed quantification of the elements, while atomic mapping permitted visualizing their distribution along the surfaces. UV-visible spectroscopy and first-principles calculations using density functional theory (DFT) were conducted, and a thorough investigation of the optical and electronic properties of the pure material upon Nd3+ insertion was provided. Electrical properties collected at room temperature revealed a growing conductivity upon doping ratio increase with a simultaneous enhancement in the carrier concentrations and mobility. The findings of the present work will help facilitate the synthesis procedure of large-area stannous-based perovskite oxide thin films through simple and efficient chemical solution methods for optoelectronic device applications.

Complex interplay of interatomic bonding in a multi-component pyrophosphate crystal: K2Mg (H2P2O7)2·2H2O.

The electronic structure and interatomic bonding of pyrophosphate crystal K2Mg (H2P2O7)2·2H2O are investigated for the first time showing complex interplay of different types of bindings. The existing structure from single-crystal X-ray diffraction is not sufficiently refined, resulting in unrealistic short O─H bonds which is rectified by high-precision density functional theory (DFT) calculation. K2Mg (H2P2O7)2·2H2O has a direct gap of 5.22 eV and a small electron effective mass of 0.14 me. Detailed bond analysis between every pair of atoms reveals the complexity of various covalent, ionic, hydrogen bonding and bridging bonding and their sensitive dependence on structural differences. The K--O bonds are much weaker than Mg--O bonds and contributions from the hydrogen bonds are non-negligible. Quantitative analysis of internal cohesion in terms of total bond order density and partial bond order density divulges the relative importance of different types of bonding. The calculated optical absorptions show multiple peaks and a sharp Plasmon peak at 23 eV and a refractive index of 1.44. The elastic and mechanical properties show features unique to this low-symmetry crystal. Phonon calculation gives vibrational frequencies in agreement with reported Raman spectrum. These results provide new insights indicating that acidic pyrophosphates could have a variety of unrealized applications in advanced technology.

Effect of damaged vehicle evacuation on traffic flow with open boundaries.

The effects of the damaged car evacuation (P(exit)) and the collision (P(col)) probabilities on the traffic flow behavior of a car accident are investigated in the one-dimensional cellular automaton Nagel-Schreckenberg model, with injecting (alpha) and extracting (beta) rates in parallel dynamics. In this study, we suppose that the car involved in collision is evacuated from the road, with an exit probability P(exit). It is found that the behaviors of density, current, and (alpha,beta) phase diagram topology depend strongly on the values of P(exit) and P(col). Indeed, the high-density region shrinks when increasing P(exit). Moreover, the critical value alpha(c)(beta), at which the low-density-high-density transition occurs, increases when increasing P(col) and/or P(exit). Furthermore, the critical value at which the transition high-density-low-density occurs decreases when increasing beta and increases with alpha.