Advanced Theory and Simulations最新文献

Barium(II) (Ba[II]) ion activation considerably increases quartz recovery, reaching up to 99.85%, as shown by micro-flotation studies. Ba(II) ions preferentially adsorb onto the quartz surface, creating active sites through electrostatic interactions that facilitate sodium oleate (NaOL) adsorption, as demonstrated by zeta potential measurements. Chemical adsorption is confirmed by Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy. Electronic density difference and density of states studies reveal strong electron transport between Ba and O, forming persistent chemical bonds. By combining chemical bonding and physical adsorption, Ba(II) ions improve NaOL adsorption on the quartz surface, offering a theoretical foundation for flotation.

The structure of three-step quantum well is receiving attention to improve the response of nonlinear optical coefficients. Here we investigate second harmonic generation produced in an asymmetric three-step quantum well by exploiting both structural parameters and external fields for maximizing the value of response aiming at elucidating the value of parameter regulation. Regarding structural parameters, variations in central barrier thickness and well width induce multiple resonance peaks in the second-order nonlinear susceptibility, attributed to quantum confinement effects and energy level spacing modifications. Electric fields induce Stark shifts that alter wavefunction overlap and dipole matrix elements, while magnetic fields introduce Landau quantization that interacts with structural asymmetry to generate additional nonlinear polarization. The SHG induced by asymmetric three-step quantum well is theoretically studied for the first time, demonstrating that the resonance peak of the second harmonic coefficient changes significantly by adjusting the parameters within a certain range. Our findings can be of interest in parameter design and experimental applications of optoelectronic devices for the selection of the more appropriate nonlinear optical configuration.

This study offers a comprehensive first-principles study on the electrical, thermodynamic, and optical characteristics of the cubic perovskite CsTaO₃ and CsNbO₃ with an emphasis on their potentials in energy conversion applications. We systematically analyze their electronic band structures using DFT with the GGA; improved by hybrid functional corrections (HSE06). The bandgaps predicted by HSE06 are 2.42 (0 GPa) and 1.67 eV (100 GPa) for CsTaO₃, whereas GGA-PBE yields 1.43 and 0.94 eV, respectively. In comparison to 1.36 and 1.01 eV with GGA-PBE, the band gaps for CsNbO₃ are 1.59 (0 GPa) and 1.32 eV (100 GPa) with HSE06. Direct bandgap in the visible region, and optical calculations indicate that CsNbO₃ can be used for photovoltaic systems and photocatalysis. A solar cell model of CsXO₃ (X = Ta, Nb) exhibits the band alignment of charge transport layers and substantial optical absorption throughout the visible range, suggesting a high potential for solar-to-electric conversion. The results of this study indicate that the optimized device on CsNbO₃ could achieve an outstanding power conversion efficiency (PCE) of 28.79%, which is higher than PEC of CsTaO₃ (25.47%). These materials can be theoretically understood through this study, resulting in energy harvesting and conversion technologies, especially photocatalysis and photovoltaics.

The paper provides a detailed exploration of piezoelectric transducers in the context of transmission and harvesting ultrasonic energy underwater through integrated theoretical study, finite element analysis, and experimental studies. The piezoelectric transducer is utilized in underwater wireless power transmission (UWPT) research and applications are commonly constructed in the form of a circular wafer. First, this paper demonstrates a way of analyzing maximum potential difference in different piezoelectric materials, such as PZT-based and lithium niobates, in COMSOL Multiphysics software. The purpose of the following analysis is to identify the maximum potential difference obtained in the case where relative permittivity depends on the applied pressure. Second, frequency dependent impedance and efficiency have been determined by driving analytic expressions of the constitutive equations of the electrical equivalent circuit (Thevenin) model. Third, a new type of UWPT process is suggested where a piezoelectric wafer transducer is used to create a connection between the transmitter and the receiver sections in an underwater setting. The ultrasonic transducer of the circular wafer type has been subjected to a finite element analysis (FEA) to assess the stress distribution, electric potential coupling, acoustic pressure fields, sound pressure fields and radiation patterns at varying excitation frequencies (20–80 kHz). Fourth, input and output properties of the proposed model, and electrical equivalent circuit model are simulated in COMSOL software. Lastly, the experimental data proves and validates the simulation and theoretical outcomes. The finding shows that the proposed model is an accurate and comprehensive description of resonance, energy transmission and harvesting in the system. This research improves the performance of Underwater Wireless Power Transfer (UWPT) systems. This is achieved by developing a refined equivalent circuit that precisely models the full process, from ultrasonic wave transmission and piezoelectric reception to final energy harvesting. This study has immersed theoretical implications and practical recommendations for future UWPT studies.

A comprehensive first-principles and machine-learning-assisted study of the oxychalcogenide BaTa₄Te₃O₁₇, highlighting its promise as a multifunctional material for thermoelectric, optoelectronic, and photocatalytic applications. Density functional theory (DFT) calculations show a direct bandgap of 3.3 eV with mixed dispersive and flat valence/conduction states, promoting anisotropic carrier transport. The effective electron and hole masses along the Γ–Γ direction exhibit more balanced carrier masses (m_e^* = 0.682 m₀, m_h^* = 0.714 m₀), corresponding to a reduced mass of 0.348 m₀, a binding energy of 260 meV, and a Bohr radius of 6.48 Å, signifying weaker exciton confinement. Thermoelectric analysis yields a Seebeck coefficient of 1029.23 µV K⁻¹ and a figure of merit ZT ≈ 0.94 at 300 K, improving at higher temperatures. The band-edge positions align well with the hydrogen evolution potential, suggesting photocatalytic suitability. To complement DFT results, supervised regression models (XGBoost and ensemble-stacking) predict E_g ≈ 3.3 eV (R² = 0.55) and ZT ≈ 0.94 with >90% accuracy. This integrated DFT–ML framework demonstrates a cost-effective route for screening and optimizing heteroanionic oxychalcogenides for next-generation energy and electronic applications.

Sodium antiperovskites have emerged as promising cathode materials for next-generation sodium-ion batteries owing to their structural flexibility and high sodium content. In this work, we present a comprehensive first-principles investigation of point defects and sodium diffusion in defect containing Na-rich antiperovskites ($��{\mathrm{Na}}_2�\mathrm{TMSO}�$, where TM = 3d transition metals). The formation energies of Frenkel (Na, S, O, and transition metal) and Schottky ($��{\mathrm{Na}}_2�O�$ and $��{\mathrm{Na}}_2�S�$) defect pairs are systematically evaluated under neutral charge conditions to elucidate the intrinsic defect chemistry and thermodynamic stability. Among all defect types, TM-Frenkel and Na-Frenkel pairs exhibit the lower formation energies, suggesting their predominance under equilibrium conditions. The energy above hull calculation (2–97 eV/atom) suggests that the Na-Frenkel defect containing structures are metastable. The influence of Na-Frenkel defects on sodium migration is further explored through diffusion pathway analysis using climbing image nudged elastic band method, revealing reduced activation barriers and enhanced Na mobility in the defected lattice, especially along (011) direction. Finally, interfacial thermodynamics between these Na-antiperovskite cathodes with Na-Frenkel defect pairs and representative solid electrolytes are examined to assess chemical compatibility and interphase stability. These results provide atomistic insight into defect-mediated ionic transport and interfacial stability, guiding the design of high-performance Na-antiperovskite-based cathodes.