Haijun Hou

This study presents a comprehensive first-principles investigation-based on the generalized gradient approximation (GGA-PBE) approach- into the physical properties of novel perovskite-type hydrides, FrXH₃(X: Ca, Sr, and Ba), with a focus on their potential for hydrogen storage applications. The obtained lattice parameters for the cubic crystal structure were calculated as 4.6396, 4.7922, and 5.1287 Å for FrCaH₃, FrSrH₃, and FrBaH₃, respectively. The structural stability of FrXH₃(X: Ca, Sr, and Ba) were confirmed through negative formation energies and favorable elastic constants, indicating both thermodynamic and mechanical stability. To further assess thermal stability, dynamics simulations were conducted, revealing no structural distortions or decomposition, thereby confirming their robustness under thermal conditions. Electronic band structure and density of states analyses revealed that all three compounds exhibit direct band gaps of 2.13, 1.96, and 1.64 eV for FrCaH₃, FrSrH₃, and FrBaH₃, respectively. Various optical properties-including optical conductivity, dielectric function, energy loss function, refractive index, and absorption were also computed. These optical characteristics suggest that FrXH₃ compounds hold strong potential for use in optoelectronic devices, photonic applications, and energy storage systems. Furthermore, the hydrogen storage capacities were calculated as 1.14, 0.96, and 0.83 wt % for FrCaH₃, FrSrH₃, and FrBaH₃, respectively. These results underscore the potential of these materials for application in hydrogen storage systems and associated technologies.

To elucidate the pressure dependence of orthorhombic Mo ₂ BC properties, this study employs density functional theory (DFT) to investigate its mechanical, electronic, lattice dynamic, and thermal behavior. The obtained lattice parameters and elastic properties of Mo ₂ BC exhibit strong agreement with existing theoretical findings. The band structure calculations reveal that orthorhombic Mo ₂ BC maintains metallic behavior under pressures spanning 0–50 GPa. Mo ₂ BC demonstrates mechanical (Born stability criteria) and dynamic stability up to 50 GPa, with elastic constants and moduli exhibiting a monotonic increase with applied pressure. Notably, pressure induces a brittle‐to‐ductile transition in Mo ₂ BC within the 10–50 GPa. In‐plane profiles of linear compressibility, shear modulus, and Young's modulus coupled with surface structural analyses highlight that anisotropy intensifies with increasing pressure. Furthermore, thermal properties (Gibbs free energy [ F ], internal energy [ E ], entropy [ S ], and heat capacity [ C _V ]) under combined high‐temperature and high‐pressure conditions were systematically investigated.

Calcium carbonate (CaCO₃) has attracted considerable attention owing to its structural versatility and broad applications in materials science and geochemistry. In this study, we employed Density Functional Theory (DFT) simulations to systematically investigate the structural, elastic, and dynamic properties of trigonal CaCO₃ under hydrostatic pressures ranging from 0 to 1.2 GPa. The optimized lattice constants closely align with previous theoretical and experimental values, thereby confirming the reliability of the computational approach. Mechanical stability was validated across the entire pressure range, with elastic constants and moduli demonstrating gradual increases under compressive strain. Elastic anisotropy was rigorously quantified using universal anisotropy indices, three-dimensional surface visualizations, and directional projections of elastic moduli. These analyses revealed pronounced pressure-dependent anisotropy. Furthermore, optical properties, including refractive indices and dielectric functions, were analyzed to clarify pressure-induced variations in electromagnetic interactions. These findings offer valuable insights into the pressure behavior of CaCO₃, advancing its potential applications in advanced functional materials and geophysical research.

This work explores the physical properties of the MAX-phase material Cr₃AlC₂ through the application of density functional theory (DFT). The refined lattice parameters were determined through the minimization of the total energy. In order to explore the electronic properties and bonding features, we carried out computations on the band structure and charge density distribution. The calculated elastic constants (C_ij) validated the mechanical stability of Cr₃AlC₂. To assess the material’s ductility or brittleness, we calculated Pugh’s ratio, Poisson’s ratio, and Cauchy pressure. The hardness was determined. This study examined the anisotropic behavior of Cr₃AlC₂ using directional analyses of its elastic properties and by computing relevant anisotropy indicators. We examined several key properties of Cr₃AlC₂, including the Grüneisen parameter, acoustic characteristics, Debye temperature, thermal conductivity, melting point, heat capacity, Helmholtz free energy, entropy, and internal energy. Phonon dispersion spectra were analyzed to assess the dynamic stability of Cr₃AlC₂.

Nb₂C has attracted particular attention in the field of elevated temperature, wear resistance, and corrosion resistance, owing to its unique physical and chemical properties. Currently, fewer efforts have been devoted to the exploration of its mechanical properties and thermodynamic response under elevated pressure. As a solution, theoretical calculations were employed to reveal the influence of increased pressure on the structural, mechanical, electronic, and thermodynamic properties of Nb₂C. Elastic moduli were derived from elastic constants, whereas Poisson's ratio, sound velocity, and Debye temperature were determined using the obtained elastic moduli and constants. The investigation focused on the analysis of elastic anisotropy through the utilization of various indexes for elastic anisotropy, as well as the construction of three‐dimensional (3D) surfaces and their planar projections. The analysis of the electronic characteristics indicates that Nb₂C displays a metallic behavior. Moreover, the hardness H_v and thermal conductivity k were evaluated by different methods.

Its outstanding mechanical and thermodynamic characteristics make SrAl₂O₄ a highly desirable ceramic material for high-temperature applications. However, the effects of elevated pressure on the structural and other properties of SrAl₂O₄ are still poorly understood. This study encompassed structural, elastic, electronic, dynamic, and thermal characteristics. Band structure calculations indicate that the direct band gap of SrAl₂O₄ is 4.54 eV. In addition, the Cauchy pressures provide evidence of the brittle characteristics of SrAl₂O₄. The mechanical and dynamic stability of SrAl₂O₄ is evident from the accurate determination of its elastic constants and phonon dispersion relations. In addition, a comprehensive analysis was conducted of the relationship between specific heat and entropy concerning temperature variations.

The development of efficient heterojunction photocatalysts with a facilitated charge carrier separation rate and improved light-harvesting capacity is still a challenging issue for effectively solving environmental pollution. Herein, a one-step refluxing process was employed to construct 2D/2D CdIn₂S₄/In₂S₃ (CISI) heterojunction photocatalysts with an intimate interface between these two components. The crystal structure, morphology, light-harvesting capacity, and Cr(VI) photoreduction performance were systematically investigated and discussed in detail. The tight interface formed between CdIn₂S₄ (CIS) and In₂S₃ (IS) could effectively facilitate the charge carrier separation and transfer. Thus, the resulting CISI composites exhibited a high efficiency for Cr(VI) photoreduction under visible light, with the optimal sample of 0.5 CISI. The charge transfer kinetics were deeply investigated by multiple techniques. Based on the characterization results, a possible mechanism for Cr(VI) photoreduction was proposed.

A two-dimensional layered CeO₂/Bi₂O₃ composite was synthesized by microwave solvothermal method. X-ray diffraction (XRD), Raman spectroscopy, field emission scanning electron microscope (FESEM), transmission electron microscope (TEM), UV-Vis diffuse reflection spectroscopy (DRS), and X-ray photoelectron spectroscopy (XPS) were used to studied crystal structure, morphology, optical performance, elemental composition and the surface electronic state of the samples. The photocatalytic properties of the prepared samples were evaluated by photocatalytic desulfurization under visible light. When the molar ratio of Ce and Bi was 1:2, CeO₂/Bi₂O₃ composite presented the highest photocatalytic desulfurization rate. Transient Photocurrent measurement, electrochemical impedance spectroscopy (EIS) and photoluminescence spectroscopy (PL) showed that CeO₂ and Bi₂O₃ formed a heterojunction, which could promote the separation of photogenerated electrons and holes, improving the photocatalytic activity. Furthermore, it was found that the active species of hydroxyl radical (·OH) played an important role in the photocatalytic degradation of dibenzothiophene (DBT) based on the active species capture experiment. Finally, a plausible mechanism for the photocatalytic oxidative desulfurization of this nanocomposite was proposed.