Chemical Physics最新文献

In this article, the structural, mechanical, electronic, optical, thermal, and thermodynamic properties of Ba₂XSbO₆ (X=P, As) double perovskite oxides were investigated by using first-principles calculations. The results show that the Goldsmith’s tolerance factor and octahedral factor of the two perovskites are in a stable range, the binding energy and formation energy are negative, and the elastic constants meet the Born-Huang stability criterion. These results suggest the stability of the two perovskite oxides. The mechanical property study indicates that Ba₂XSbO₆ (X=P, As) exhibits high bulk modulus and shear modulus. Poisson’s ratio (ν) and the elastic anisotropy index (A) suggest that they are anisotropic ductile materials. The electronic properties show that Ba₂PSbO₆ and Ba₂AsSbO₆ are indirect bandgap semiconductors with bandgap values of 2.130 eV and 1.596 eV, respectively. The optical properties show that Ba₂XSbO₆ (X=P, As) has excellent light absorption capacity in the range of 2.5–30 eV. Specifically, Ba₂AsSbO₆ has a higher absorption capacity for visible light compared to Ba₂PSbO₆. Thermodynamic properties show that the Debye temperature of the two perovskites is higher than 420 K, the melting points is higher than 1700 K, the minimum lattice thermal conductivities is close to 1, and the specific heat reaches the Dulong-Petit limit at about 700 K. This study shows that the double perovskite oxide Ba₂XSbO₆ (X=P, As) has important potential in the field of thermoelectricity and optoelectronics.

Based on first-principles calculation, we investigated the properties of toxic gases (CO, H₂S, NH₃, NO₂, SO₂) adsorption on different sides of monolayer SnSSe. Results show that all the toxic gas molecules tend to adsorb on the hollow sites above Sn. The adsorption energies of all the gas molecules are negative, ranging from −0.1026 eV to −0.2494 eV, suggesting that the adsorption of the gases is spontaneous. We also calculated the charge transfer between the gas molecules and the SnSSe. The results showed that all the gas molecules were charge donors except NO₂. The recovery time of the adsorption of toxic gases on the monolayer SnSSe are also discussed through the transition state theory, and the results showed that the adsorption times of these gas molecules were below the millisecond level. Calculations of electronic properties show that the adsorption of NO₂, NH₃ changes the electronic structure of SnSSe near the Fermi level, while the remaining gases have little effect on the electronic structure of monolayer SnSSe near the Fermi energy level, demonstrates the potential of monolayer SnSSe for N-based gas detection. Our study is expected to provide theoretical guidance for the fabrication of SnSSe-based gas-sensitive sensor devices and performance improvement.

NADFP·DMF has good detonation performance, mechanical sensitivity and high thermal decomposition temperature. Current studies on NADFP·DMF have been carried out at ambient temperature and pressure, and its properties under pressure have yet to be analysed in depth. By using the generalized gradient approximation (GGA) plane-wave norm conserving pseudopotential method based on the framework of density functional theory, the structural, mechanical, electronic and thermodynamic properties of the monoclinic crystal system NADFP·DMF under 0–20 GPa are calculated. The calculations show that the lattice parameters decrease with increasing pressure. The structure is mechanically stable and ductile within 0–20 GPa. We analyzed electronic properties, including band structure and density of states. NADFP·DMF is a direct band gap compound only at 15 GPa, and the band gap decreases with increasing pressure, resulting in an increase in sensitivity. In addition, the thermodynamic properties of NADFP·DMF are investigated, including enthalpy, temperature*entropy, Gibbs free energy, Debye temperature and heat capacity.

The catalytic and photocatalytic performance of TiO₂ in air pollutant degradation is significantly influenced by the adsorption of water. Here, we explore the molecular mechanism of formic acid and formaldehyde decomposition and their interaction with water on the TiO₂ (1 1 0) surface, employing density functional theory (DFT) calculations and reactive molecular dynamics (RMD) simulations. RMD simulations indicate that due to the competitive adsorption of water at the surface Ti site, formic acid predominantly exists in a monodentate dissociative adsorption form on the TiO₂ (1 1 0) surface. Moreover, on the TiO₂ (1 1 0) surface, water molecules inhibit the adsorption and dissociation of formic acid, but they facilitate that of formaldehyde, forming methanediol (*CH₂OHO) and dioxymethylene (*CH₂O₂). DFT calculations suggest that the formation pathway of *CH₂OHO or *CH₂O₂ is energetically favorable, but the formation of formate is difficult. This contrasts with the adsorption of formaldehyde on the anatase surface, where formate species are formed.

The electronic absorption spectra of CuH and AgH molecules are calculated using the analytical expression for the spectral density related to the thermal dipole time correlation function. In addition, the vibronic transition probabilities between the initial and final states are determined by calculating the transition dipole moments and the Franck-Condon factors using the LEVEL program. The spectroscopic constants recently obtained from MRCI + SOC calculations are used to calculate the absorption spectral line shapes of CuH and AgH molecules and plotted in the time and frequency domains for the vibronic transitions from the ground state Ω = 0⁺(I) to the excited states Ω = 0⁺(II), 0⁺(III), 1(I), 1(II), 1(III), and 1(IV) for CuH and to the excited states Ω = 0⁺(II), 0⁺(III), 0⁺(IV), 1(II), 1(III), 1(IV), 1(V), and 1(VI) for AgH.

The communalization of all-polymer solar cells depends on the cost of active layer materials. We have introduced a framework to find the easily synthesizable polymers. Breaking Retrosynthetically Interesting Chemical Substructures (BRICS) method is used to generate a large database of polymers and synthetic accessibility of generated polymers is predicted. The generated database is visualized using various methods. Energy levels of polymers are also predicted using pretrained machine learning models. Polymers are screened on the basis of predicted properties. Library of polymers are displayed using the T-distributed Stochastic Neighbor Embedding (t-SNE) visualization. Structure Activity Landscape Index (SALI) visualization is also used. A significant change is observed in synthetic accessibility score on structural changes. The histagradient boosting regressor is used to predict the energy levels of polymers that energy levels play significant role in the selection of materials for organic photovoltaic cells. Synthetic accessibility of polymers is analyzed and a significant number of polymers are easy to synthesize. Thirty polymers are selected through screening process that are potential candidates for organic photovoltaic cells.

An effective method for fabricating flexible materials containing thermally conductive fillers, such as hexagonal boron nitride (hBN), utilizes plasma surface modification and polyrotaxane (PR) with movable cross-linking points. This study demonstrated that lowering the coverage rates of PR composites increased the mobility of the cross-linking points. Plasma surface modification improved the dispersion of hBN and enabled homogeneous deformation of the PR composites owing to movable cross-linking points. Studying the deformation with a model including a finite extension effect indicated that the sliding range in the low-covered PR composites was extended compared to that in the high-covered PR composites, resulting in a smaller Young’s modulus, longer extension, and higher toughness.

The adsorption of pyrazinamide (PZA) drug by the assistance of FeC₂₀, FeC₁₉, and FeC₁₈ iron-decorated metallofullerenes were analyzed using density functional theory (DFT) calculations regarding the drug delivery developmental issues. Formations of PZA@FeC₂₀, PZA@FeC₁₉, and PZA@FeC₁₈ conjugated systems were analyzed by the structural and electronic features. Meaningful adsorption strengths were found for the models with a priority of PZA@FeC₂₀ conjugation formation with an exterior iron atom of the metallofullerene. Three configurations were found for each conjugation mainly along with the existence of O…Fe and O…N interactions and a complementary H…C interaction. Hence, the conjugated systems could show a suitable “recovery time” for providing the sensing function along with the changes of “conductance rate” levels. Indeed, the results indicated the formation of observable conjugated systems, in which the conjugations and configurations could be employed regarding a customization towards the drug delivery of PZA antibiotic in a smart mode.

Nitric acid (HNO₃) has a critical impact on air pollution and herein a new mechanism of HNO₃ from the NO₂ + ClO reaction with (H₂O)_1-2 was found. The quantum chemical results in the gas phase showed that H₂O acting as a reactant can interact with NO₂ and ClO to form HNO₃ through a chain-like mechanism. The rate ratio indicated that the participation of a single H₂O molecule in the NO₂ + ClO reaction is more important than that of (H₂O)₂, and this reaction can compete with the hydrolysis of N₂O₅ within the 15–50 km altitude range at night. BOMD simulations at the air–water interface indicated that NO₂ + ClO reaction to form HNO₃ followed a single-water mechanism. The nucleation simulations illustrated that HNO₃ tends to form stable clusters with H₂SO₄, NH₃ and H₂O molecules. This work determines the significance of the NO₂ + ClO reaction with (H₂O)_1-2 and gives a new potential route of HNO₃ in highly polluted coastal regions.