Gallium oxide is increasingly used in a variety of applications, but confusion reigns over the Brillouin zone and the band structure of monoclinic β‐Ga2O3. We present a detailed study of the shape of ...the Brillouin zone and the location of high‐symmetry points. Combined with a study of electronic structure based on hybrid density functional theory, this allows us to derive an accurate band structure. We discuss the nature of the band gap and the location of the band extrema.
In this work, we have employed the first‐principles calculations to investigate the phase stability and mechanical and optoelectronic characteristics of Hf2AX (A═Al, Si and X═C, N) MAX phases. Phase ...stabilities of Hf2AX compounds have been evaluated by the formation enthalpy computations and phonon dispersion curves, which indicate that all studied compounds are structurally and dynamically stable. The mechanical stability has been determined by elastic stiffness constants, which confirms that the studied MAX phases are mechanically stable. The computed results for Pugh's and Poisson ratios indicate the brittle nature of Hf2AX MAX phases. It is interesting to note that Si‐based MAX phases possess high values of B/G, indicating that they are harder than Al‐based compounds. The obtained band structures and partial density of states indicate the metallic character of all Hf2AX compounds. The strong hybridization of d‐orbitals of Hf with p‐orbitals of N and the comparatively weaker hybridization of p‐orbitals (Hf) with Al/Si p‐orbitals is observed. The presence of pseudogaps near the Fermi energy level emerges due to the orbital hybridization involving Hf, Al/Si, and C/N atoms. The analysis of charge density difference maps reveals the presence of a strong covalent bond between the Hf and C/N atoms, whereas a relatively weaker covalent bond is seen between the Hf and Al/Si atoms. Furthermore, numerous optical characteristics have been investigated to account for the behavior of the Hf2AX compounds to those of impinging electromagnetic rays. The highest absorptivity is noticed within the energy range of 7.5–12.5 eV. The optical spectra in the range of 1.7 eV (IR) to 9 eV ultraviolet (UV) have been observed for the investigated MAX phases, predicting their suitability as proficient energy absorbers within the UV region. The Intriguing properties of Hf2AX compounds are anticipated to be appropriate materials for a variety of applications.
In this paper, we study a few versions of the uncertainty principle for the windowed Opdam–Cherednik transform. In particular, we establish the uncertainty principle for orthonormal sequences, ...Donoho–Stark's uncertainty principle, Benedicks‐type uncertainty principle, Heisenberg‐type uncertainty principle, and local uncertainty inequality for this transform. We also obtain the Heisenberg‐type uncertainty inequality using the
‐entropy of the windowed Opdam–Cherednik transform.
An intricate sea-urchin-like hexagonal WO3 nanostructure was synthesized by a facile hydrothermal approach. Sensing properties of the as-fabricated sensor exhibited surpassing response and ...selectivity for NO2 in comparison of H2 after corroborating the composition, phase-purity and surface morphology using X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Formation of the urchin-like structure was ascribed to the capping effects of potassium sulfate that prompts the anisotropic growth of WO3, leading to hierarchical complex with a large surface-volume ratio. In particular, first-principle calculation had provided a new perspective for us to delve into the sensing process of H2 and NO2 from an atomic level. It was found that the sensing properties mainly arose from the tuning of electronic structure and electrons transfer between the adsorbed gas and the sensitized surface along with the charge relocation between them. Finally, a plausible mechanism was proposed as theoretical guidance for achieving high-performance sensors experimentally and supposedly.
The electrochemical stability window of solid electrolyte is overestimated by the conventional experimental method using a Li/electrolyte/inert metal semiblocking electrode because of the limited ...contact area between solid electrolyte and inert metal. Since the battery is cycled in the overestimated stability window, the decomposition of the solid electrolyte at the interfaces occurs but has been ignored as a cause for high interfacial resistances in previous studies, limiting the performance improvement of the bulk‐type solid‐state battery despite the decades of research efforts. Thus, there is an urgent need to identify the intrinsic stability window of the solid electrolyte. The thermodynamic electrochemical stability window of solid electrolytes is calculated using first principles computation methods, and an experimental method is developed to measure the intrinsic electrochemical stability window of solid electrolytes using a Li/electrolyte/electrolyte‐carbon cell. The most promising solid electrolytes, Li10GeP2S12 and cubic Li‐garnet Li7La3Zr2O12, are chosen as the model materials for sulfide and oxide solid electrolytes, respectively. The results provide valuable insights to address the most challenging problems of the interfacial stability and resistance in high‐performance solid‐state batteries.
The thermodynamic electrochemical stability windows of Li10GeP2S12 and Li7La3Zr2O12 are calculated using first principles computation method, and also experimentally validated using a Li/electrolyte/electrolyte‐carbon cell developed by us. Both solid electrolyte materials have narrower electrochemical windows than previously claimed by the battery community. These results can provide valuable information to address the most challenging interfacial problem for high‐performance all‐solid‐state batteries.
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