The Journal of Physical Chemistry A最新文献

A recruiting rate (k_rc) of 0.1-5 s^-1 has been proposed as the criterion for super-resolution spontaneously blinking rhodamines. Accurate prediction of the recruiting rate (k_rc) of rhodamines is very important for developing spontaneously blinking rhodamines. However, as far as we know, there is no reliable theoretical method to predict the k_rc. Herein, we meticulously investigated the effect of intermolecular hydrogen bonds on the spirocyclization reactions of rhodamines. Moreover, a theoretical descriptor (ΔE_C-T) was proposed to reliably assess the k_rc. ΔE_C-T quantified the ring-opening energy barrier of spirocyclization reactions. A robust linear correlation was established between theoretical ΔE_C-T values and experimentally k_rc values. Based on this correlation, we designed and screened five spontaneously blinking sulfonamide rhodamine dyes with optimized k_rc values. We expected that these findings could enable the targeted design of spontaneously blinking rhodamines.

We present ab initio calculations of the resonant Auger spectrum of benzene. In the resonant process, Auger decay ensues following the excitation of a core-level electron to a virtual orbital. Hence, resonant Auger decay gives rise to higher-energy Auger electrons compared to nonresonant decay. We apply equation-of-motion coupled-cluster (EOM-CC) methods to compute the spectrum in order to explain the main features in the experimental spectrum and to assess the capability and limitations of the available theoretical approaches. The results indicate that participator decay can be well described with the Feshbach-Fano approach based on EOM-CC wave functions in the singles and doubles (SD) approximation, but spectator decay is more difficult to describe. This is because the target states of spectator decay are doubly excited, resulting in the need to include triple excitations in the EOM-CC wave function. Resonant Auger decay in benzene is thus a challenging test case for EOM-CC theory. We examine the performance of different noniterative triple corrections to EOM-IP-CCSD and our numerical results highlight the need to include triple excitations iteratively.

When dielectrics are hit with intense infrared (IR) laser pulses, transient metalization can occur. The initial attosecond dynamics behind this metallization are not entirely understood. Therefore, simulations are needed to understand this process and to help interpret experimental observations of it, such as with attosecond transient absorption (ATA). In this paper, we present first-principles simulations of ATA based on bulk-mimicking clusters and real-time time-dependent density functional theory (RT-TDDFT), with Koopmans-tuned range-separated hybrid functionals and Gaussian basis sets. Our method gives good agreement with the experiment for the breakdown threshold in silica and diamond. This breakdown voltage corresponds to a Keldysh parameter of approximately one and thus involves a transition to a regime where the dynamics are driven by tunneling. Pumping at an amplitude just below this value causes a mixture of multiphoton and tunneling excitations across the band gap to occur. The computed extreme ultraviolet and X-ray attosecond transient spectra also agree well with the experiment and show a decrease in optical density due to the transient population of the conduction band from the IR field. First-principles approaches such as this are valuable for interpreting the complicated modulations in a spectrum and for guiding future attosecond experiments on solids.

In this study, we worked at the CCSD/aug-cc-pVTZ level to obtain the conformers of glycine in its neutral and zwitterionic forms in the gas and water phases. We then computed the NMR properties (spin-spin coupling constants and nuclear magnetic shieldings) at the SOPPA/aug-cc-pVTZ-J level. We attempt to elucidate the apparent discrepancy arising from two previous works by Valverde et al. [J. Chem. Phys., 2018, 148, 024305] and Caputo and Provasi [Sci, 2021, 3, 41]. Our optimized structures align with previous theoretical predictions, although some geometries were not found. Additionally, our results suggest that in the gas phase the Δ ¹J(O,C) = ¹J(O_cis,C_O) - ¹J(O_trans,C_O) is positive when the acid group is in the trans conformation and negative in the cis conformation; however, this trend is not well reproduced in water. From magnetic shielding calculations, we cannot distinguish between an O-H in the cis or trans conformation.

DNP (3,4-dinitropyrazole) has attracted much interest due to its promising melting characteristics and high detonation performances, such as low melting point, high density, high detonation velocity, and low sensitivity. In this work, first-principles molecular dynamics (MD) simulations were performed to investigate the anisotropic shock response of DNP in conjunction with the multiscale shock technique (MSST). The initial decomposition mechanism was revealed through the evolution of the chemical reaction and product analysis. Independent gradients based on the Hirshfeld partition (IGMH) method showed that van der Waals forces mainly exist between the layered structures. Chemical reaction analyses revealed four major initial decomposition reactions for the DNP molecule. At different shock velocities, the molecules in $\left(\overline{1}01\right)$ were more inclined to undergo H dissociation reactions, whereas the molecules in $\left(\overline{1}0\overline{1}\right)$ were more inclined to undergo nitro-dissociation reactions. Product analysis showed that the faster the shock velocities, the earlier the DNP molecules completely disappeared. Furthermore, N₂ and CO₂ were mainly produced by the ring-opening reaction, and their numbers in $\left(\overline{1}01\right)$ were higher than in $\left(\overline{1}0\overline{1}\right)$, indicating that the ring-opening reaction was more easy to occur in $\left(\overline{1}01\right)$. The ring-opening reaction mainly occurred in $\left(\overline{1}01\right)$, suggesting that $\left(\overline{1}01\right)$ was more decomposable than $\left(\overline{1}0\overline{1}\right)$. The fitting results of the state equation showed that the theoretical detonation pressures for $\left(\overline{1}01\right)$ and $\left(\overline{1}0\overline{1}\right)$ are close to the experimental value. These results could help to increase the understanding of shock-induced anisotropy in energetic materials.

Plasmon resonance plays an important role in improving the detection of biomolecules, and it is one of the focuses of research to use metal plasmon resonance to achieve fluorescence enhancement and to improve detection sensitivity. However, the problems of nondynamic tuning and fluorescence quenching of metal plasmon resonance need to be solved. Graphene surface plasmon resonance can be dynamically controlled, and the graphene adsorption of fluorescent molecules can avoid fluorescence quenching and greatly improve the fluorescence emission intensity. The graphene-metal hybrid structure designed in this work can solve the above two problems well, and the plasmon resonance can improve the fluorescence emission efficiency of molecules on the surface of graphene and improve the sensitivity of biological detection. At the same time, graphene nanoribbons in our hybrid structure do not require patterning, which greatly lowers the threshold for graphene application in biosensing.

We introduce the first version of GPU4PySCF, a module that provides GPU acceleration of methods in PySCF. As a core functionality, this provides a GPU implementation of two-electron repulsion integrals (ERIs) for contracted basis sets comprising up to g functions using the Rys quadrature. As an illustration of how this can accelerate a quantum chemistry workflow, we describe how to use the ERIs efficiently in the integral-direct Hartree-Fock build and nuclear gradient construction. Benchmark calculations show a significant speedup of 2 orders of magnitude with respect to the multithreaded CPU Hartree-Fock code of PySCF and the performance comparable to other open-source GPU-accelerated quantum chemical packages, including GAMESS and QUICK, on a single NVIDIA A100 GPU.

Recently, we investigated a number of so-called σ- and τ-functionals based on the adiabatic-connection fluctuation-dissipation theorem (ACFDT); particularly, extensions of the random phase approximation (RPA) with inclusion of an exchange kernel in the form of an antisymmetrized Hartree kernel. One of these functionals, based upon the approximate exchange kernel (AXK) of Bates and Furche, leads to a nonlinear contribution of the spline function used within σ-functionals, which we previously avoided through the introduction of a simplified "top-down" approach in which the σ-functional modification is inserted a posteriori following the analytic coupling strength integration within the framework of the ACFDT and which was shown to provide excellent performance for the GMTKN55 database when using hybrid PBE0 reference orbitals. In this work, we examine the analytic "bottom-up" approach in which the spline function is inserted a priori, i.e., before evaluation of the analytic coupling strength integral. The new bottom-up functionals, denoted σ↑AXK, considerably improve upon their top-down counterparts for problems dominated by self-interaction and delocalization errors. Despite a small loss of accuracy for noncovalent interactions, the σ↑AXK@PBE0 functionals comprehensively outperform regular σ-functionals, scaled σ-functionals, and the previously derived σ+SOSEX- and τ-functionals in the WTMAD-1 and WTMAD-2 metrics of the GMTKN55 database.