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[Display omitted] • A comprehensive calculation and analysis of defect properties in the corundum, monoclinic, and orthorhombic Ga 2 O 3 phases are presented. • The Ga-rich growth environment in all Ga 2 O 3 phases favors the spontaneous formation of oxygen vacancies with concentrations that can reach as high as 1021 cm−3. • The antisite defects contribution in intrinsic defect density is not negligible in an O-rich environment, and can reach a concentration of 1014 cm−3. • The charge transition levels in all phases are at deep levels within the bandgap. • Raman spectroscopy in an as-grown β-Ga 2 O 3 and a high temperature annealed β-Ga 2 O 3 reveals an increase in point defect concentration, correlating the defect formation energies to experimental observation. Ultrawide bandgap gallium oxide (Ga 2 O 3) is a promising material for power semiconductor devices and deep ultraviolet (UV) solar-blind photodetectors. Understanding the properties of point defects in Ga 2 O 3 is necessary to realize better-performing devices. A comprehensive study based on density functional theory (DFT), using the generalized gradient approximation (GGA): Perdew-Burke-Ernzerhof (PBE) exchange–correlation functional, of point defects in corundum (α), monoclinic (β), and orthorhombic (ε) phases of Ga 2 O 3 is presented. The point defects include vacancies, interstitials, antisites, and extrinsic impurities in various phases of Ga 2 O 3. Defect formation energies, charge transition energy levels, and defect concentrations variation with temperature are listed and presented under both gallium-rich (Ga-rich) and oxygen-rich (O-rich) growth conditions. The formation energy diagrams predict that the Ga 2 O 3 phases favor the formation of Ga and O vacancies and the incorporation of extrinsic impurities. The calculations also show that the charge transition levels are deep inside the bandgap regardless of the Ga 2 O 3 phase and growth environment. The impacts of temperature on the intrinsic point defects are analyzed by probing the vibrational modes of β-Ga 2 O 3 thin films grown in a metal–organic chemical vapor deposition (MOCVD) system at 700 °C temperature and annealed at 1100 °C in an O-rich environment. [ABSTRACT FROM AUTHOR]

Magnesium ion batteries (MIBs) are one of the vital strategies for the next-generation energy needs and computational simulations can accelerate this search many folds. In this paper, we suggest a novel cathode material, quinone functionalized hexahydroxytriphenylene (HHTP) and diphenylbutadiynebis (boronic acid) (DPB) based porous polymer (QHHTP-DPB), for Mg-ion batteries. The material is stable with highly porous structure and strong affinities for Mg ions to attach to C=O sites of the quinone rings. The single unit of the polymer layer can be fully loaded with Mg ions at various active sites exhibiting a specific theoretical-capacity of 720.48 mAhg−1 and positive low open-circuit voltage of 0.39 V. No structural variation is observed in QHHTP-DPB and a larger decrease in the HOMO-LUMO gap occurs after Mg ions adsorption onto the polymer, reflecting the better cycling performance and high capacity for Mg ion batteries. These results show that our designed quinone functionalized HHTP-DPB porous polymer could be a futuristic cathode material for MIBs and needs further theoretical and experimental investigations. [Display omitted] • QHHTP-DPB based porous polymer is studied for Mg-ion batteries. • The QHHTP-DPB polymer significantly stored a maximum of 10 Mg ions. • The QHHTP-DPB has high specific capacity of 720.48 mAh/g. [ABSTRACT FROM AUTHOR]

[Display omitted] • Benzoquinone-based microporous polymer is designed as cathode for magnesium-ion batteries that exhibits high stability. • Strong anchoring capability of magnesium ions with polymer have larger binding energies. • The polymer has high storage capacity i.e. twelve Mg ions without any structure distortion/volume change. • The material has high specific capacity of 467.038 mAh/g versus previously reported cathode materials for magnesium-ion batteries. Rechargeable magnesium-ion batteries (MIBs) can fulfill large-scale energy storage needs due to the abundance of Mg but technical challenges due to complexity of its chemistry results uncertainties about their commercialization. We for the first report benzoquinone-based microporous conjugated polymer (BQMCP) as cathode material for MIBs using density functional theory. It is dynamically and thermodynamically stable with a strong affinity for Mg-ions. The Mg ions strongly attaches to the C O group (redox-active sites) than π-bonds of BQMCP. The binding energy demonstrates that the interaction of the 2 Mg-ion system (BE = −47.32 kcal.mol−1) is stronger than the mono-Mg ion system (BE = −39.57 kcal.mol−1). The attachment of first Mg2+ to the BQMCP facilitate the attachment of another Mg ion. The BQMCP shows higher positive redox potential, which decreases with the increase of Mg atoms with the high storage capacity of twelve Mg ions/ BQMCP unit at redox-active sites without any structure distortion. Mg ions successfully entraps in bulk porous stacked BQMCP layers with higher negative binding energy values. The results demonstrates that the BQMCP is a promising cathode material for magnesium ion batteries in future. [ABSTRACT FROM AUTHOR]

In this work, spin-polarized density functional theory calculations are conducted to evaluate the possible applicability of a single Si atom doped boron nitride graphyne-like nansoheet (Si@BN-yne) for reduction of nitrous oxide (N 2 O). The calculations show that Si-doping in BN graphene is energetically favorable, and the resulting Si@BN-yne is both dynamically and thermodynamically stable. According to our findings, N 2 O spontaneously dissociates when it interacts with the Si@BN-yne from its O site without the need for an energy barrier, releasing 2.89 eV of energy. The adsorption energy of CO molecule on the Si@BN-yne is less negative than that of N 2 O, implying that N 2 O will predominately occupy the catalyst surface. The CO + O ad reaction is used to remove the remaining oxygen atom (O ad) from the Si@BN-yne surface. The calculations show that the reaction proceeds through a low energy barrier of 0.05 eV, which is much lower than the previously reported catalysts. This demonstrates the high catalytic activity of Si@BN-yne nanosheet. Furthermore, the adsorption of H 2 O and O 2 species on the Si@BN-yne nanosheet is investigated. The results show that the presence of these species has no effect on the catalytic activity of the Si@BN-yne for N 2 O reduction. These results show that the proposed novel Si@BN-yne catalyst can be regarded as an efficient material in the development of promising active catalysts for N 2 O elimination from the environment. [Display omitted] • Si-doping modifies the electronic structure of BN-yne. • N 2 O interacts weakly with the pristine BN-yne. • N 2 O dissociates spontaneously over Si@BN-yne. • The activation barrier for removing O ad from Si@BN-yne is 0.05 eV. [ABSTRACT FROM AUTHOR]