Physical Chemistry Chemical Physics最新文献

The stereodynamical control of resonance profoundly influences the outcomes of molecular collisions. Here, we perform time-dependent wave packet calculations for the Cl + H₂ (v = 1, j = 1) → HCl + H reaction to investigate how stereodynamical control influences reaction resonances. The results of the dynamical calculations indicate that the backward scattering differential cross section of the HCl (v′ = 2) product exhibits two pronounced peaks at collision energies of ∼0.4 eV and ∼0.5 eV. Analysis confirms that these characteristic peaks are attributable to reaction resonances. This work explores the impact of different alignment angles of the H₂ reactant molecule on these two reaction resonances. It is found that the parallel alignment of the H₂ molecule markedly amplifies the intensity of the resonance peaks, while the perpendicular alignment results in a notable suppression of these features. Furthermore, the alignment angle of the reactants significantly influences the scattering direction of the products. Products at the energies of resonances from the head-on collision tend to scatter in the backward direction. In contrast, those from the side-on collision are more likely to scatter forward and sideways.

Water radiolysis plays an important role in elucidating radiation-induced biological effects such as early DNA damage induction, chromosome aberrations, and carcinogenesis. Several Monte Carlo simulation codes for water radiolysis, commonly referred to as chemical simulation codes, have been developed worldwide. However, these codes typically require substantial computational time to calculate the time-dependent G values of water radiolysis species (e.g., ˙OH, e⁻_aq, H₂, and H₂O₂), and their application is often limited to specific ion beam types. In the Particle and Heavy Ion Transport code System (PHITS), the track-structure mode that allows the simulation of each atomic interaction in liquid water for any charged particles and the subsequent chemical code (named PHITS-Chem code) dedicated to electrons was developed previously. In this study, we developed the PHITS-Chem code to support a broader range of ion beam species. To reduce computational time, we introduced new features including a space partitioning method to increase the detection efficiency of reactions between chemical species and a radical scavenger model that reduces the lifetime of OH radicals. We benchmarked the updated PHITS-Chem code by comparing its predicted time-dependent G values for protons, α particles, and carbon ions with those reported in the literature (i.e., other simulation and measured data). The inclusion of a space partitioning method and the modified OH radical scavenger model reduced the time required by the PHITS-Chem code to calculate G values (by approximately 28-fold during radiolysis simulations under 1-MeV electron exposure) while maintaining calculation accuracy. A key advantage of the PHITS-Chem code is the four-dimensional visualization capability, integrated with PHITS′ native visualization software, PHIG-3D. Considering the ability of the PHITS-Chem code to handle OH radical scavengers (i.e., tris(hydroxymethyl)aminomethane and dimethyl sulfoxide), it is anticipated to offer precise and intuitive insights into the radiation-induced biological effects of chemical species in ion-beam radiotherapy.

Two-dimensional monoelemental materials have emerged as promising candidates for use in the development of next-generation optoelectronic devices. In this work, we investigate the photovoltaic effect of monolayer (ML) α-selenium p–n junctions by using ab initio quantum transport simulations. Our research results indicate that the photocurrent of the ML α-selenium p–n junction optoelectronic device exhibits anisotropy. The maximum photoresponsivity (178.49 a₀² per photon) in the armchair (ARM) direction is one-half that (341.72 a₀² per photon) in the zigzag (ZZ) direction. When stress is applied, the most significant modulation of photoresponsivity occurs in the ZZ direction, reaching a value of 613.21 a₀² per photon. When a gate voltage is applied, the most significant modulation of photoresponsivity occurs in the ARM direction, reaching a value of −684.88 a₀² per photon. When a thermal difference is applied, the most significant modulation of photoresponsivity occurs in the ARM direction, reaching a value of 412.14 a₀² per photon. Thus, ML α-selenium in the ZZ direction can be used for photodetection and photosensing, while ML α-selenium in the ARM direction can be used for photosensing. Both strain engineering and temperature differences cause a blueshift in the photocurrent as a function of energy. Our work paves the way for research into low-dimensional monoelemental-material optoelectronic devices.

We present a combined X-ray and depolarized dynamic light scattering study on a series of liquid phenylalkanes, consisting of an aromatic phenyl ring attached to an alkyl chain of varying length. We study the influence of competing interactions of rings and chains on liquid structure and molecular reorientation. The X-ray scattering curves of the investigated liquids show a weak prepeak in a q range below the main scattering peak, indicating a certain degree of structure formation on a larger length scale than commonly found in simple liquids. As a function of temperature and alkyl chain length, we find that the observed prepeak shares some characteristics with that found for ionic liquids, suggesting a similar origin, i.e., domains of ring groups separated by alkyl chains leading to nanometer-scale structuring. Furthermore, with increasing chain length, the scattering curves show a distinct transition in the temperature dependence of the prepeak amplitude, which is mirrored in the activation energy of molecular reorientation, obtained via depolarized dynamic light scattering. As a possible interpretation, we suggest that ring–ring interactions control structure as well as dynamics for short alkyl chains but rapidly lose influence above a certain alkyl chain length. Since phenylalkanes are among the most simple representatives of liquids consisting of aromatic and non-aromatic units, we regard this work as a proof of concept to study the coupling of structure and dynamics in liquids with competing interactions weaker than both Coulombic interactions and hydrogen bonding.

The emerging multi-resonance thermally activated delayed fluorescence (MR-TADF) emitters with organoboron and nitrogen cores highlight their significance in OLEDs. However, their efficiency is challenged by slower rate constants in the reverse intersystem crossing (k_RISC) process compared to conventional TADF emitters. The study entails an in-depth analysis focused on gaining a better understanding of the photophysical properties of MR-TADF emitters. Using DFT and TD-DFT analyses, 48 MR-TADF molecules are studied, incorporating heavy atoms such as sulfur and selenium, and their subsequent oxidation, and peripheral donors such as carbazole (Cz), tert-butyl-carbazole (tCz), diphenylacridine (DPAC), and dimethylacridine (DMAC) into organo boron and nitrogen-embedded systems. Moreover, the QM/MM approach was utilized to examine the excited state properties in the crystal phase. A comprehensive assessment of this molecular framework reveals that integrating heavy atoms and donors into MR-TADF molecules results in significant enhancements in ΔE_ST, larger SOC, and higher-order radiative (10⁸ s⁻¹) rates, leading to faster k_ISC (∼10⁸ s⁻¹) and k_RISC (∼10⁶ s⁻¹) rates. Based on key criteria, eight potential molecules were selected and their excited-state properties were precisely analyzed using double-hybrid density functionals including B2PLYP and PBE0-2, along with highly correlated wave function STEOM-DLPNO-CCSD.