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To investigate the protection mechanism and performance of N-phenyl-1-naphthalenamine (antioxidant A), N-phenyl-2-naphthalene (antioxidant D), and N, N'-diphenyl-1,4-phenylenediamine (antioxidant H) in the HTPB-TDI matrix, quantum chemistry (QC), molecular dynamics (MD), and Monte Carlo (MC) simulation methods were used to calculate the reaction sites, hydrogen dissociation energy, reaction energy barrier, diffusion coefficient, solubility parameters and permeation coefficient of the antioxidants and HTPB-TDI based on the density functional theory (DFT) and transition state theory (TST). The results show that the energy required for the dissociation reaction of N-H bonds in all three antioxidant molecules is less than the dissociation energy of the α-H bonds in the HTPB-TDI, and the reaction energy barriers for the reactions of all three antioxidants with peroxy radicals are also less than the reaction energy barriers for the same type reactions of HTPB-TDI; among the three antioxidants, antioxidant H has the lowest hydrogen dissociation energy and reaction energy barriers; the differences of the solubility parameters between antioxidants and HTPB-TDI are all less than 6.95 (J•cm−3)0.5, and as the temperature increases, the diffusion coefficients of the antioxidants added in the blended system continue to increase; under the same temperature conditions, the diffusion coefficient of antioxidant H is the smallest, and that of antioxidant A is the largest, which indicates that all three antioxidants have relatively good compatibility with HTPB-TDI, and antioxidant H has the best stability in the HTPB-TDI matrix. The order of solubility coefficients of O2 in HTPB-TDI containing different antioxidants is [SHTPB-TDI&A] > [SHTPB-TDI&D] > [SHTPB-TDI&H], indicating that antioxidant H has the strongest oxygen barrier ability. Based on the analysis of the migration, compatibility, oxygen barrier ability, and the difficulty of the reaction of the three antioxidants, it can be seen that the protective performance of the three antioxidants is as follows: [antioxidant H] > [antioxidant D] > [antioxidant A].

Mixed-halide perovskite quantum dots (PeQDs) are the most competitive candidates in designing solar cells and light-emitting devices (LEDs) due to their tunable bandgap and high-efficiency quantum yield. However, phase separation in mixed-halide perovskites under illumination can form rich iodine and bromine regions, which change its optical responses. Herein, we synthesize PeQDs combined with mesoporous zinc-based metal organic framework (MOF) crystals, which can greatly improve the stability of anti-anion exchange, including photo-, thermal, and long-term stabilities under illumination. This unique structure provides a solution for improving the performance of perovskite optoelectronic devices and stabilizing mixed-halide perovskite devices.

Polyethylene glycols (PEG) and toluene diisocyanate (TDI) are often used as the main components of binders and curing agents in solid propellants, and their aging is an important issue in the storage and use of propellants. To study the aging behavior and aging mechanism of nitrate ester plasticized polyether propellant (NEPE) matrix during storage, the transition states of aging reactions of binder and curing agent were optimized at the (U)B3LYP/6-311G(d,p) level of theory, and the rate coefficients over the temperature range of 298–1000 K were calculated by CVT theory. The results showed that there were five kinds of aging reactions for binder, which included decomposition, nitration, H abstraction, oxidation, and crosslinking reactions. Among them, theenergy barriers of oxidation and H abstraction reactions were relatively low (79.3–91.2 kJ·mol−1) and the main reaction types of binder aging. The main aging reaction of curing agent was decomposition. Compared with the aging reactions of binder, the energy barriers of curing agent are higher (196.6–282.7 kJ·mol−1) and the reaction is more difficult to occur. By comparing the energy barriers and rate constants of different reactions, it is found that the aging of NEPE propellant matrix can be divided into two stages. In the first stage, the propellant matrix mainly undergoes H abstraction and oxidation reaction, and as the reaction proceeds, the products crosslink to form -O-O-, -C-C-, and -C-O-C- bonds. At this time, the long chain molecules of the propellant matrix crosslink, and the molecular weight increases. This stage corresponds to the rising stage of mechanical properties in the aging process of the propellant. In the second stage, the propellant matrix mainly undergoes decomposition and nitration, resulting in degradation, the reduction of molecular weights, and the appearance of holes and microcracks in the matrix. This stage corresponds to the decline of mechanical properties in the aging process of the propellant. The above simulation results are in good agreement with the aging experimental phenomena, revealing the microscopic mechanism of the changes in the macroscopic properties of NEPE propellant during the aging process, and providing a theoretical basis for the related research on the aging properties and anti-aging technology of NEPE propellant.

Abstract The optical properties of alternating ultrathin Ti0.91O2 nanosheets and CdS nanoparticle hybrid spherical structures designed by the layer-by-layer (LBL) assembly technique are investigated. From the photoluminescence (PL) spectral measurements on the hybrid spherical structures, a spectrum-shifted fluorescence emission occurs in this novel hybrid material. The time-resolved PL measurements exhibit a remarkably increased PL lifetime of 3.75 ns compared with only Ti0.91O2 spheres or CdS nanoparticles. The novel results were attributed to the enhanced electron-hole separation due to the new type II indirect optical transition mechanism between Ti0.91O2 and CdS in a charge-separated configuration.

Mechanistic aspects of acetaldehyde hydroxylation by Compound I model active species of cytochrome P450 2E1 (CYP2E1) were investigated by means of B3LYP density function theory calculations. The results demonstrate that acetaldehyde hydroxylation by CYP2E1 is in accord with the effectively concerted mechanisms both on the high quartet spin state and on the low doublet spin state.

In this paper, we describe the approach of resonant trajectories of photon emission (Traj?N? and TrajQ) in the conformational coordinate X and external field frequency ?L space to extract the conformational information of single molecule. The Smoluchowski equation is employed to describe the conformational dynamics of the single molecule in complex environments. This approach is applied to single Thioflavin T (ThT) molecule, and our results are in excellent agreement with the results of ab initio simulations. [ABSTRACT FROM AUTHOR]

We present a detailed theoretical approach to investigate the laser-induced dissociation dynamics of a triatomic molecule on its electronic excited state in full dimensional case. In this method, the time evolution of the time-dependent system is propagated via combined the split operator method and the expansion of Chebyshev polynomials (or short-time Chebyshev propagation) and the system wave functions are expanded in terms of molecular rotational bases. As an example of the application of this formalism, the dissociation dynamics of H3+ → H²+ + H induced by ultrashort UV laser pulses are investigated on new Born-Oppenheimer potential energy surfaces. Our numerical results show that the signals of dissociation products will be easier to observe as the increasing of field strength. Driving by a 266 nm laser beam, the calculated central value of kinetic-energy-release is 2.04 eV which shows excellent agreement with the experimental estimation of 2.1 eV. When the H3+ ion is rotationally excited, the spatial distribution of product fragments will become well converged. [ABSTRACT FROM AUTHOR]

Making use of the molecular closed-orbit theory and a new model potential for the Rydberg molecule, we calculated the recurrence spectra of HeH+ molecule ion in a magnetic field for different quantum defects. The Fourier transformed spectra of HeH+ molecule ion have allowed direct comparison between peaks in the spectra and the scaled action values of closed orbits of the excited electron in the external fields. We find that the spectral modulations can be analyzed in terms of the scattering of the excited electron on the molecular core. Unlike the case of the Rydberg atom where the elastic scattering is predominant, modulations produced by inelastic scattering are also vital to the photoabsorption spectrum of Rydberg molecule. Our results are in good agreement with the quantum results, which suggest that our method is correct. [ABSTRACT FROM AUTHOR]

The equilibrium structure, spectroscopy constants, and anharmonic force field of germanium dichloride have been calculated at MP2, B3LYP, and CCSD(T) levels of theory employing two basis sets, cc-pVDZ and cc-pVTZ, respectively. The computed geometries, rotational constants, and vibration-rotation interaction constants, and quartic centrifugal distortion constants are compared with the available experimental data. The harmonic frequencies, anharmonic constants, and cubic and quartic force constants are predicted. The calculated results show that the MP2 results are in excellent agreement with experiment and represent a substantial improvement over the results obtained from B3LYP. The CCSD(T) method is also an advisable choice to study anharmonic force field of molecules. [ABSTRACT FROM AUTHOR]

Density functional cluster model computations are applied to the study the reaction of acrylonitrile with the C (001)-2x1 surfaceof diamond. It is shown that isomerization between the intradimer [4+2] product and intradimer [2+2] (sub cc) product is little more suitable than the direct path to formation of the intradimer [2+2] (sub cc) product.