Solid State Communications最新文献

Double perovskites have gathered momentous attention due to their structural, optoelectronics, and thermal properties. FP-LAPW + lo technique was employed along with the PBEsol-GGA and TB-mBJ potential. The optimized parameters and E-V parabolic curve were computed employing Birch Murnaghan's equation of state (BM-EOS). The negative formation energy E_f for Rb₂YCuCl₆ and Cs₂YCuCl₆ confirms the thermodynamic stability of these double perovskites. The mechanical stability of both compounds was confirmed by their elastic constants $C_{ij}$, Pugh's ratio, and anisotropy. The indirect band plots of Rb₂YCuCl₆ (2.57eV) and Cs₂YCuCl₆ (2.39eV) double perovskites confirm the semiconductor nature. The optical properties like dielectric function, reflectivity, optical conductivity, absorption coefficient, and energy loss function were determined within an energy range of up to 18 eV. The high absorption spectra for the under-study compounds 147.21 × 10⁴ cm⁻¹ at 14.60 eV for Rb₂YCuCl₆ and 261.30 × 10⁴ cm⁻¹ at 15.57 eV for Cs₂YCuCl₆ lies in the far UV region determines its potential use in the high-frequency devices. The thermoelectric properties such as the Seebeck coefficient, ZT, and power factor, are investigated using the semi-classical Boltzmann theory implemented in the BoltzTrap code. The peak value of ZT for Rb₂YCuCl₆ is 0.38 and for Cs₂YCuCl₆ is 0.33. The suggested findings indicate that Rb₂YCuCl₆ and Cs₂YCuCl₆ are potential candidates for thermoelectric and photovoltaic applications.

We use time-dependent Ginzburg–Landau theory in a three-dimensional model, including thermal noise, to analyze angle-dependent Hall resistivity and longitudinal resistivity of type-II superconductor. The Hall resistivity and longitudinal resistivity are calculated as functions of temperature, magnetic field and the angle $\theta$ between the magnetic field and the ab-plane in the vortex-liquid regime. Our theoretical calculations within a self-consistent fluctuation approximation for MgB₂ and HgBa₂CaCu₂O₆ materials are in good agreements with the experimental findings for both below and above the critical temperature $T_c$. We observe that when the field angle decreases, the transition temperature increases and the magnitude of longitudinal resistivity decreases, which is qualitatively comparable to decrease of the perpendicular field component. However, when the magnetic field direction approaches the layer surface, it shows a clear different effect from that of a perpendicular field with the same normal component.

Occupancy tendencies of elements significantly differ in precipitation-strengthened Ni-based, CoNi-based, and Co-based alloys, which further affect the γ/γ′ lattice misfit and mechanical properties, but relevant research is lacking. In this work, occupancy tendencies of doping elements (Ta, W, Cr, Fe, Mo, Re, Ti, V) and lattice misfit of γ and γ′ phases in precipitation-strengthened alloys dependent on Co/CoNi ratios have been systematically studied through first-principles calculations. The results show that the tendency of all eight elements to occupy the γ′-Al sublattice site increases with the increase of the Co/CoNi ratio, and the tendency to occupy the γ-Ni/Co site all decreases. The occupancy tendencies of these elements exhibit a strong correlation with the Co/CoNi ratio. Lattice misfit gradually increases as the Co/CoNi ratio is raised. Notably, element Ta has the greatest influence on lattice misfit. The appropriate Co/CoNi ratio is conducive to synergistically enhancing high entropy effects and lattice distortion effects for matrix and Ni₃Al precipitate phase, and regulating reasonable lattice misfit, which is beneficial for the design of precipitation-strengthened alloys with excellent strength-ductility balance.

Doping is an effective strategy to modulate the electronic performance of materials by forming new chemical bonds and relaxing the neighboring bonds, which may change catalytic performance of materials. Herein, we demonstrate the effects of a series of nonmetal (NM) dopants on the electronic properties and photocatalytic activity of g-GaN monolayer using first-principle calculations. NM dopants prefer to substitute N atom under Ga-rich condition. C, O and F doped specimens are highly stable under both Ga-rich and N-rich conditions. NM dopants induce the generation of impurity levels, contributing to reduce the electronic transition energies. S, Se and Te doped specimens increase by about 11, 8 and 4 times for absorption intensity in the region of visible light, respectively. Remarkably, S, Cl, Se, Br, Te and I dopants can effectively decrease the recombination rate of photogenerated electrons and holes of the g-GaN in photocatalytic reaction. H, B, C Si, P and As doped system can induce more active sites. Remarkably, halogen dopants could increase the both redox and reduction ability of g-GaN monolayer. Thus, NM dopants can effectively tune redox potential of g-GaN monolayer and improve its photocatalytic performance.

We theoretically investigate the nonlinear effects of a magnetic field on the relaxation process of exciton–polaritons toward Bose–Einstein condensation in GaAs quantum wells. Our study reveals that the modification of the exciton’s effective mass, Rabi splitting, and dispersion significantly alters the relaxation rate of polaritons as they approach condensation. By employing a quasi-stationary pump, we clarify the dynamics of the total and condensed polariton populations in response to varying magnetic field strengths. Notably, we demonstrate that under low-energy pumping conditions, the presence of a magnetic field significantly suppresses condensation. This suppression is attributed to the decreased scattering rate between energy levels, which is a consequence of the reduced steepness in the high-energy dispersion. Conversely, increasing both the pump energy and the magnetic field can enhance relaxation efficiency, leading to a substantially larger number of condensed polaritons.

This study presents the prediction of a novel 2D nanostructure, C₆O₂, characterized as a direct bandgap semiconductor with a rectangular atomic arrangement. Employing computational codes based on density functional theory (DFT), we optimized the lattice parameters, yielding (a = 6.26 Å and b = 2.43 Å). Stability analysis, including cohesive energy (with a value of −7.85 eV/atom) and phonon dispersion within the first Brillouin zone, confirms the acceptable stability of the C₆O₂ structure. Electronic properties in the ground state were investigated using both HSE06 and GGA approaches. Our results indicate that the predicted structure exhibits a direct bandgap with energy values of 0.108 eV (PBE), 0.11 eV (mBJ), and 0.415 eV (HSE06) at the M point. Furthermore, we explored the optical properties of this nanostructure using the HSE06 approach. Notably, the ground state exhibits moderate absorption across the visible light spectrum (around 3–5 eV) and a low reflection rate. These findings suggest that C₆O₂ holds promise for future experimental endeavors in designing electro-optical applications.

Nitrogen oxides (NO_x) are known for having a significant greenhouse effect and provoking several health issues. Because of that, it is necessary to find an effective manner to remove them from polluted air. In this study, samarium-doped titania was synthesized via sol-gel using two different synthesis routes and varying the calcination temperature and the Sm³⁺ content. The main difference between the two syntheses was the pH solution. The acidic pH favored the presence of the anatase crystalline phase, the most photoactive and interesting for photocatalytic applications. Furthermore, these catalysts were evaluated in a lab-scale UV photoreactor following the NO conversion via chemiluminescence, according to the ISO standard 22197–1. The Sm content positively affected the NO removal. The highest NO conversion was 92 %, with the doped titania obtained at a calcination temperature of 500 °C and with 0.5 % wt. of samarium. This result was congruent with the reported literature's energy bandgap estimated (2.98 eV).

In this study, both ferromagnetic and antiferromagnetic spin configurations of a 2D-centered tetragonal Ising nanoparticle with two types of exchange interactions (J and Jr) are considered. A newly introduced algorithm using Cellular Automata simulation method, which is relied on counting the states with a magnitude of magnetization per site exceeding a threshold value m_t, is used to compute the value of the reduced critical temperature. The sensitivity of the critical temperature value to the lattice size and exchange interactions (The ratio of Jr/J denoted by r parameter) are examined. The results show that the value of the critical temperature increases with increasing lattice size with a decreasing slope. Moreover, the same behavior was observed in ferromagnetic and antiferromagnetic cases.