Chemical Physics最新文献

Efficient hydrogen storage materials are essential for the advancement of sustainable energy solutions. This work employs density functional theory (DFT) to examine the capacity of XInH₃ (X = Rb and Cs) as materials for storing hydrogen in solid-state. The crystal structures of RbInH₃ and CsInH₃, which both belong to the space group pm3m, with lattice parameters of 4.35 Å and 4.44 Å, respectively. The formation enthalpies of RbInH₃ and CsInH₃ are −4.29 eV/atom and −6.41 eV/atom, respectively, suggesting that they possess favorable thermodynamic stability. The gravimetric hydrogen storage capacities of RbInH₃ and CsInH₃ are 1.45 % and 1.18 % respectively. An examination of the electronic structure indicates the presence of metallic properties, characterized by the overlapping of the valence and conduction bands. The optical characteristics of RbInH₃ and CsInH₃ demonstrate substantial absorption in the ultraviolet (UV) region, with RbInH₃ having a peak at 20.25 electron volts (eV) and CsInH₃ at 16.92 eV. The mechanical properties demonstrate anisotropic behavior and imply brittle features. The evaluation also includes thermodynamic properties such as the Debye temperature and melting temperatures. These findings suggest that RbInH₃ and CsInH₃, with their favorable structural stability and ease of synthesis, could be integrated into current hydrogen storage technologies, offering a pathway for further optimization to enhance their practical applicability.

In this work, we investigate the adsorption of single-component and binary neutral fluids in cylindrical pore using molecular dynamics simulations combined with classical density functional theory (cDFT). For the binary case, we also consider scenarios where one component exhibits a non-spherical structure. We investigated the density distribution curves of fluid components in the pore and found that the cDFT calculations without any adjustable parameter yielded results consistent with molecular dynamics simulations. This consistency becomes more pronounced as the temperature increases. At lower temperatures, the theoretical accuracy declines, but it still remains quantitatively reliable. We have developed a method for calculating diffusion coefficient in porous media involving exchange of particles between the exterior and interior of the pores, and applied the method to compute the diffusion coefficients for molecules from outside to inside the pore, as well as within the pore itself. Based on the calculated diffusion coefficients, we can draw several main conclusions: intrapore diffusion along the axial direction always decreases with increasing pore radius; increasing the surface force field strength enhances diffusion in narrow pores while reducing it in wider pores. Moreover, increasing the attraction strength between particles consistently leads to slower diffusion. These findings provide valuable insights into the factors affecting the diffusion process and can be used to optimize porous materials for various applications.

The hydroxylammonium ionic liquids (ILs) falling within the category of protic ionic liquids (PILs) have garnered attention from researchers, owing to their outstanding solubility properties. A one-step method was employed to synthesize a series of ethanolamine ILs. The thermodynamic properties of the ILs, including surface tension, density, and electrical conductivity, were measured across varying temperatures. Essential parameters such as thermal expansion coefficient, molecular volume, surface entropy, and surface energy were estimated using empirical equations. In order to elucidate the intermolecular interactions within the ethanolamine carboxylate ILs, the sigma profiles of ILs were determined using COSMO-RS. It was observed that the ethanolamine cation has a strong potential as a H-bond donor, while the carboxylate anion demonstrates significant capability as a hydrogen bond acceptor. By DFT calculations, it was observed that the NH in the ethanolamine cation can form H-bonds with the oxygen atom in the carboxylate anion.

An improved Wei potential energy function as a molecular potential model has not been widely reported probably due to its physical structure. In this study, the Feinberg–Horodecki (FH) equation is examined for the improved Wei energy potential function. To validate the calculations, the Feinberg–Horodecki equation is transformed into an energy equation by putting $c=1,$ and $P_n=E_n.$ Numerical results are generated for some molecules using the energy equation and the molecular spectroscopic constants for $\lambda =-0.1,0,$ and 0.1. The predicted results for the energy eigenvalues are compared with the experimental data for four halogen molecules and four gallium halides. The results revealed that the negative values of $\lambda$ do not produce values that align with the experimental data. It is also shown that the result obtained with $\lambda =0$ reproduces a better result for the improved Wei potential energy function than the result obtained with $\lambda =0.1.$

This study reports the structural, electronic, optical, phonon, thermodynamic and thermoelectric properties of ${\mathrm{AgYF}}_3$ (X=Mg, Sr) for photovoltaic and energy applications. We performed first principles calculations using full potential linearized augmented plane wave, FP-LAPW method implemented in Wien2k. The generalized gradient approximations of Perdew–Burke–Ernzerhof PBE-GGA, and PBE revised for solids, PBEsol, is employed for structural optimization of these lead free halide perovskites. The Birch–Murnaghan energy volume curve fitting comprehend the structural stability. The optimized lattice constant of ${\mathrm{AgMgF}}_3$ and ${\mathrm{AgSrF}}_3$ obtained with PBE-GGA(PBEsol) is 3.99(3.92) Å and 4.42(4.65) Å. The stability is further tested with the help of formation energy and positive phonon dispersion curves calculations. For the calculations of explicit electronic and optical properties, we also employed Tran–Blaha modified Beck–Johnson (TB-mBJ) and Strongly Constrained but Appropriately Normed, SCAN, exchange and correlations functionals. The electronic band gap of ${\mathrm{AgMgF}}_3$ computed with PBEsol, TB-mBJ and SCAN is 1.96 eV, 5.25 eV and 2.59 eV exhibiting M-$\Gamma$ indirect band gap. The band gap energy of ${\mathrm{AgSrF}}_3$ is 2.06 eV, 6.42 eV and 2.70 eV with PBEsol, TB-mBJ and SCAN. The indirect band gap nature of ${\mathrm{AgSrF}}_3$ is confirmed by PBEsol and TB-mBJ while it anticipated direct band gap behavior with meta-GGA SCAN. The different optical parameters like dielectric constant, optical conductivity, energy loss function, absorption, reflectivity and refractive index are calculated to assess optical activity of both perovskites. Comprehensive electronic and optical analysis advocates the utility of ${\mathrm{AgMgF}}_3$ and ${\mathrm{AgSrF}}_3$ for different applications is solar technology and optoelectronic devices.

The unique structural properties of two-dimensional materials make them promising for energy storage applications. This work theoretically predicts for the first time that Monolayer VOPO₄ (MNL VOPO₄), exfoliated from the delithiated phase of tetragonal LiVOPO₄, is stable at room temperature, exhibiting excellent thermodynamic and kinetic stability, thus making it a promising high-capacity anode material for sodium-ion batteries (SIBs). Compared to bulk VOPO₄, the monolayer structure significantly reduces the sodium ion migration energy barrier from 1.006 to 0.0795 eV, thereby markedly enhancing sodium ion migration kinetics. MNL VOPO₄ can adsorb up to 32 sodium ions, corresponding to a theoretical capacity of 634.88 mA h g⁻¹ and an energy density of 895.18 Wh kg⁻¹. Furthermore, the excellent structural stability of MNL VOPO₄ favors its cycling performance during charge and discharge processes. This work provides theoretical insights for better utilizing and developing multi-atomic phosphate compounds as electrode materials for secondary batteries.

Gadolinium silicate, (Gd₂SiO₅) co-doped with Ce and Eu has been found to exhibit enhanced luminescence efficiency, which makes it a promising material for use in scintillators and phosphors. It has excellent scintillation properties such as high density and high Zeff. In this study, we used density functional theory (DFT) calculations within the Wien2k software to investigate the effect of Ce and Eu concentration and native defects on the electronic structure and optical properties of Ce and Eu co-doped Gd₂SiO₅. We utilized the DFT + U method to treat the localized 4f electrons of Ce and Eu. Our results indicate that the electronic structure and optical properties of Ce and Eu co-doped Gd₂SiO₅ are significantly affected by the concentration of the dopants and presence of native defects. We found that increasing the concentration of Ce and Eu dopants leads to a shift in the bandgap to lower energies, resulting in enhanced absorption and emission spectra. Moreover, our calculations reveal that presence of oxygen vacancies and Gd interstitials can induce new defect levels in the bandgap, which may affect the luminescence properties of the material. Our study provides valuable insights into the atomic-level mechanisms that govern the luminescence properties of Ce and Eu co-doped Gd₂SiO₅ which can aid in the design and optimization of luminescent materials for various applications.

Dye-sensitized solar cells (DSSCs) are cost-effective photovoltaic devices that convert solar energy into electricity using a dye sensitizer, TiO₂ photoanode, electrolyte, and counter electrode. This study investigates the impact of substituents on the performance of naphthoquinone-based dye sensitizers in DSSCs. We analyzed various naphthoquinone derivatives’ electronic structures and light absorption properties using DFT and TD-DFT. Our results demonstrate that electron-donating groups enhance DSSC performance by improving light absorption and electron injection. Specifically, naphthoquinone derivatives with methoxy (Dye-2) and methyl (Dye-3) groups showed superior properties. TD-DFT analysis revealed high molar extinction coefficients over a broad spectrum, making these dyes efficient at capturing sunlight. Additionally, these dyes effectively interact with TiO₂, which is crucial for photostability and photovoltaic performance. In conclusion, naphthoquinone derivatives with electron-donating groups significantly improve DSSC performance, with Dye-2 and Dye-3 being strong candidates for high-performance applications.

The surface relaxations, surface stability, electronic structures, and equilibrium morphology of D5₂-La₂O₃ were analyzed by means of first-principles calculations. The stoichiometric surfaces of D5₂-La₂O₃ possess thermodynamic energies of the following order: (0 0 1) < (1 1 0) < (1 0 0). Changes in temperature and the partial pressure of oxygen were employed to determine the energy of the non-stoichiometric surfaces. The results indicated that the energies of the (ns-1La1O)-terminated (1 0 0) and (ns-1La)-terminated (0 0 1) surfaces increased with increasing oxygen partial pressures and decreased with temperatures, whereas the (ns-1O)-terminated (0 0 1) and (ns-1O)-terminated (1 0 0) surfaces exhibited the reverse rule. According to the calculated density of states, surface relaxations primarily impact the surface electronic structures. The Gibbs-Wulff model was used to forecast the equilibrium morphology of D5₂-La₂O₃, which followed in comparison with other’s experimental findings.

It is indisputable that structural defects are pivotal in modulating the properties of materials. This study provides a comprehensive analysis of the structural, optical, and photoluminescence characteristics of V₂O₅, ZrO₂, and ZrV₂O₇.These materials were chosen for their potential applications in various key technological domains. The XRD results revealed the formation of high-purity materials with no secondary phases. It was determined that ZrO₂exhibits the most significant quantity of structural defects among the investigated materials. The variation in crystallite size as determined by XRD aligns with the variation in grain size observed through Scanning Electron Microscopy (SEM).The optical band gaps of V₂O₅, ZrO₂, and ZrV₂O₇ were determined to be 2.27 eV, 5.19 eV, and 2.38 eV, respectively. X-ray Photoelectron Spectroscopy (XPS) analysis indicated the presence of constituent elements without any contaminants. A detailed examination of the photoluminescence (PL) emission characteristics in both UV–Vis and near-infrared (NIR) regions for all materials presented broad visible luminescence in the [450–650] nm range under UV excitation. Structural defects are crucial in determining the physico-chemical properties of materials. This is thoroughly examined for V₂O₅, ZrO₂, and ZrV₂O₇.The infrared (IR) emission spectra, introduced for the first time in this study for V₂O₅, ZrO₂, and ZrV₂O₇, are employed to elucidate the localization of structural defects within the band gap.