Chemical Physics最新文献

Understanding the carrier recombination processes in Sb₂Se₃ is essential for its optoelectronic applications. In this work, carrier recombination dynamics in Sb₂Se₃ were studied by broad band transient absorption spectroscopy. Firstly, the contribution of photothermal effect to the transient absorption spectrum was thoroughly discussed. It is confirmed that the excited state absorption (ESA) band with lifetime of several nanoseconds results from co-contribution of photo thermal effect and deep trapped carrier absorption. Secondly, the features of transient absorption spectrum on picosecond time scale were interpreted. The short-lived ESA band around 1000 nm was assigned to shallow trapped carrier absorption, while not band gap renormalization (BGR) or free carrier absorption. By globally fitting the transient absorption spectrum, the hot carrier cooling time and time constant for free carrier relax into deep trap state were determined to be 0.25∼0.45 ps and 3.1∼8.7 ps, respectively. Finally, we built up the carrier recombination model of Sb₂Se₃. The experimental results in this work will improve the understanding on the carrier recombination in Sb₂Se₃.

Titanium dioxide (TiO₂) is a semiconductor material that widely used in numerous applications due to its exceptional physical and chemical properties. This study explores the structural, electronic and elastic properties of TiO₂ phases in rutile, anatase and brookite under hydrostatic pressure up to 100 GPa. At 0 GPa, the computed lattice parameters and volumes align closely with experimental data. The band structure reveals that rutile and brookite exhibit direct band gaps while anatase shows an indirect band gap. Elastic properties including bulk modulus, shear modulus, Young’s modulus, Cauchy pressure, Pugh ratio and Poisson’s ratio were calculated using the Voigt-Reuss-Hill approximation. Our findings confirm the mechanical stability of all TiO₂ phases and offer insights that align with existing theoretical and experimental data. These findings provide a comprehensive understanding of behavior of TiO₂ under high-pressure condition which is crucial for optimizing its applications in various fields such as photocatalysis and solar cells.

The boiling point is a crucial indicator for assessing the suitability of insulating gases. Its theoretical prediction has consistently garnered significant attention from the scientific community. In this study, a boiling point database composed of hexa-element (C, H, O, N, F, S) for potential insulating gases was constructed. The model of Gradient Boosting Regression with RDKit descriptors (RDKit-GBR) achieved superior predictive ability on the test set with a coefficient of determination of 0.97, a mean absolute error of 17.74 °C, and a root-mean-squared error of 27.83 °C. The SHapley Additive exPlanations analysis showed that the “Ipc” feature in RDKit, which represents the spatial relationship and interaction between pairs of atoms within molecules, plays a central role in predicting the boiling points for insulation gases. Furthermore, the applicability of RDKit-GBR method was further validated across several elemental combinations. Eventually, compared with the previously reported models, the hexa-element model achieves excellent accuracy.

This work investigates the photoelectrochemical performance of an FTO (Fluorine-doped Tin Oxide) /WO₃ (tungsten trioxide) /BiVO₄ (bismuth vanadate) /TiO₂ (titanium dioxide) photoanode for water splitting. By forming a heterojunction between WO₃ and BiVO₄, charge separation and transportation are significantly enhanced, resulting in an improved photocurrent density. Surface modification with a thin TiO₂ layer further improves the stability of the photoanode without compromising its photocurrent. The SEM, XRD, and XPS analyses confirm the successful formation of the photoanode structure. The photoelectrochemical J-V curves demonstrate that the WO₃/BiVO₄ composite electrode outperforms single WO₃ and BiVO₄ electrodes, and the TiO₂ coating further enhances its performance. These findings provide valuable insights into optimizing BiVO₄-based photoanodes for efficient hydrogen production via water splitting.

Several fourth-order symmetric operator-splitting schemes with four and five stages for solving the time-dependent Schrödinger equation have been proposed. These schemes have been studied and compared with some optimal fourth- and sixth-order operator split schemes reported in the literature using a one-dimensional model and several realistic three-dimensional triatomic reactive scattering problems in Jacobi coordinates. Two new fourth-order operator-splitting schemes with four and five stages, which are more efficient than previously reported schemes, are recommended for the realistic numerical solution of the time-dependent Schrödinger equation in the field of molecular dynamics. It was found that the order-preserving method proposed by McLachlan works well for three-dimensional triatomic reactive scattering problems in Jacobi coordinates, despite the complicated form of the Hamiltonian.

The purpose of this study is to examine the structural, electronic, optical, and thermoelectric features of novel double perovskite Cs₂YCuX₆ (X=Cl, Br, and I) for the first time in order to look for potential applications in solar power systems. Using first-principles calculations based on the widely recognized Density Functional Theory (DFT) and the PBE-Generalized Gradient Approximation (GGA) functional included in the WEIN2k package, the characteristics of the perovskites were determined. From the results of band structure and Total Density of States (TDOS) the energy band gap of Cs₂YCuCl₆, Cs₂YCuBr₆, and Cs₂YCuI₆ are observed 2.34 eV, 2.03 eV and 1.68 eV respectively. The PDOS outcomes shows that the formation of the valance and conduction bands is due to the hybridization of Cu-3d and halogen ions such that (X=Cl, Br, and I). The calculated values of goldsmith’s tolerance factor and formation energy reveal that the examined halide perovskites are structurally and thermodynamically stable. The electron localization function ELF and bader charge analysis show that the ionic nature between Cs and halogen ions X. Regarding the optical behavior, Cs₂YCuI₆has shown maximum absorption of electromagnetic radiation and conductivity in the ultraviolet and visible region i.e. (128–471 nm) which makes it a suitable candidate for optoelectronic and solar cell applications. The thermoelectric properties of the studied compounds have been calculated by means of the Boltztrap code. The presented findings unveil that amongst all studied compoundsCs₂YCuI₆ is best candidate for solar cell and thermoelectric applications due to higher conductivity, larger absorption range, significant Seebeck coefficient and higher Power factor.

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.

Calculation of nonlinear spectra of chromophore aggregates using response function theory when the number of contributing chromophores is large, and the level of excitation is high is extremely complicated. The main limitation is due to the exponential growth of computational time due to the aggregate size and number of excitations when considering an arbitrary excitation intensity. Non-perturbative calculation of spectra in this case becomes advantageous. We revisit our proposed model with exciton - exciton annihilation terms and apply it to large aggregates. We generalize the equations for both paulions and bosons with a parameter that allows smooth transition from one description to another. Intermediate statistics may also be valuable as molecular electronic excitations do not strictly obey either boson or paulion statistics. Specific approximations allow efficient calculation of pump-probe spectra for a large J aggregate.