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The stability of W–C compounds (WC)-type ReC has been controversial for many years. Here, based on ab initio algorithm, we systematically searched for stable structures in the rhenium–carbon (Re–C) system at 0–300 gigapascal (GPa) pressure and analyzed the phase diagram within the pressure range. Only P63/mmc-Re2C, C2/m-Re3C, P21/m-Re4C, and C2/m-Re5C2 phases are found to be stable under 0–300 GPa, while WC-type ReC has high enthalpy and does not appear in the phase diagram. We also discussed the stability of WC-type ReC. Among these structures, C2/m-Re3C, P21/m-Re4C, and C2/m-Re5C2 are hitherto unknown structures, which could maintain dynamic and mechanical stability under ambient pressure. In addition, through the analysis of the structural and mechanical properties, P63/mmc-Re2C is the hardest metal among them with 31.5 GPa Vickers hardness at 0 GPa, and the metastable P 6 ¯ m 2 -Re5C3 has the second-highest hardness (29.3 GPa), both of which exceed the hardness of TiN (18.7 GPa), the commercial material used for cutting tools. The study of Re–C compounds with high hardness provides theoretical guidance for further experimental research. [ABSTRACT FROM AUTHOR]

High-hardness metal compounds have huge potential applications in multifunctional devices used under extreme conditions. Here, an ab initio evolutionary algorithm was used to systematically search for structures in the Re3C system with high hardness and metallicity under the pressure of 0–300 gigapascal (GPa). We discovered a structure (namely, C2/m) with the lowest enthalpy at 154 GPa and two metastable phases (namely, P63/mmc and C2/m- α), which could maintain thermodynamic and mechanical stability at zero pressure, and they could be quenched to ambient conditions. More importantly, the hardness of the metal compounds (21.4 GPa for C2/m, 25.2 GPa for P63/mmc) exceeds that of TiN (18.7 GPa), the material for commercial machine tools. In addition, our analysis shows that the coexistence of Re–C bond and Re–Re bond with strong coupling, and avoiding the antibonding state of 5d-electron of Re–Re bond near the Fermi level, could be the reasons why the structure has high hardness and metal properties at the same time. [ABSTRACT FROM AUTHOR]

Dy-Bi co-doped yttrium tungstate crystal materials were synthesized by high temperature solid-state method. To reveal the photoluminescence features and properties of the samples, some measurements have been taken. It turned out that different Bi concentrations play obvious influence in emission performance, and show visible light emission under ultraviolet light excitation. Besides, the effect of temperature on phase structure of samples has also been studied here. Superhigh X-ray luminescence of the phosphors exhibited the promising application in the field of high energy detection. The X-ray irradiation crystal resistance stability of the phosphors has also been investigated through the subsequent testing of XRD and spectra. [ABSTRACT FROM AUTHOR]

Solar cell is a kind of devices for renewable and environmentally friendly energy conversion. One of the important things for solar cells is conversion efficiency. While much attention has been drawn to improving efficiency, the role of strain engineering in two-dimensional materials is not yet well-understood. Here, we propose a Pmc 21-As monolayer that can be used as a solar cell absorbing material. The bandgap of single-layer Pmc 21-As can be tuned from 1.83 to 0 eV by applying tensile strain, while keeping the direct bandgap characteristic. Moreover, it has high light absorption efficiency in the visible and near-infrared regions, which demonstrates a great advantage for improving the conversion efficiency of solar cells. Based on the tunable electronic and optical properties, a novel design strategy for solar cells with a wide absorption range and high absorption efficiency is suggested. Our results not only have direct implication in strain effect on two-dimensional materials, but also give a possible concept for improving the solar cell performance. [ABSTRACT FROM AUTHOR]

By employing an ab initio evolutionary algorithm, we predict two novel metastable structures whose energies are just higher than g-SiC but lower than other two-dimensional (2D) SiC siligraphenes reported so far. One is composed of 4-6-8 C–Si rings named tho-SiC siligraphene and the other one is composed of 5-6-8 rings named pho-SiC siligraphene. They are almost equal in energy, but interestingly, our calculations demonstrate that tho-SiC siligraphene is a semiconductor like g-SiC, while pho-SiC siligraphene is a 2D metal. Additionally, unlike g-SiC which is very easy to switch from a direct band gap to indirect band gap semiconductor and exhibits homogenous isotropy characteristic under biaxial strains, tho-SiC siligraphene keeps a consistently direct band gap from 1.02 eV to 1.98 eV as the uniaxial strain increases from −9% to 9% and it shows strong anisotropic electronic structures. The obtained calculation results indicate that tho-SiC siligraphene may be a better candidate than g-SiC in the application of light-emitting devices in the future. [ABSTRACT FROM AUTHOR]

Dual-functional ZnWO4:Dy3+, Bi3+ were synthesized via high-temperature solid-state reaction method. The as-prepared samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), photoluminescence spectra and photocatalytic properties. The ZnWO4:Dy3+, Bi3+ phosphor shows photoluminescence with a broad band and the feature Dy3+ emission, and a high photocatalytic activity in degradation of Rhodamine B (RhB) under simulated UV irradiation. The result shows that doping Bi3+ in ZnWO4:Dy3+ can enhance light harvest capability to generate more electron-hole pairs, and acted as a trap center by decreasing the recombination of photogenerated electrons and holes. All of the results obtained by the work suggest that ZnWO4:Dy3+, Bi3+ phosphors are promising materials for the photocatalytic decomposition of pollutants. [ABSTRACT FROM AUTHOR]