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Nonadiabatic processes play an important role at energies near or higher than conical intersection of adiabatic potential energy surfaces in chemical reactions. In this work, dynamics of the nonadiabatic H + NaD reaction at low temperatures are studied by using the quantum wave packet method based on an improved L-shaped grid. The nonadiabatic H + NaD reaction has two exothermic reaction channels: Na(3s) + HD and Na(3p) + HD; the latter can only occur

The first report of two dynamical resonances in the H + LiH+ reaction at collision energies below 10 meV is presented.

Cold and ultracold collisions are dominated by quantum effects, such as resonances, tunneling, and nonadiabatic transitions between different electronic states. Due to the extremely long de Broglie wavelength in such processes, quantum reactive scattering is most conveniently characterized using the time-independent close-coupling (TICC) methods. However, the TICC approach is difficult for systems with a large number of channels because of its steep numerical scaling laws. Here, a recently proposed quantum wave packet (WP) approach for solving adiabatic reactive scattering problems at low collision energies is extended to include nonadiabatic transitions. To impose the outgoing boundary conditions, the total scattering wavefunction is split into three parts, the interaction, the asymptotic, and the long-range regions. Each region is associated with a different set of basis functions, which could be optimized separately. In this way, an extremely long grid can be used to accommodate the characteristic long de Broglie wavelengths in the scattering coordinate. The better numerical scaling laws of the WP approach have the potential for handling larger nonadiabatic reactive systems at low temperatures in the future.

The HD molecule is an important coolant in early universe chemistry models and a tracer of H2 in star-forming regions. Rate coefficients for collisional excitation and de-excitation of HD rotational and vibrational levels form important ingredients in astrophysical models. While collisions with He, H2, and H are the most important, available data for H + HD collisions are largely limited to temperatures less than 1000 K for the vibrational ground state, low-lying rotational levels of the v = 1 HD vibrational level, or computed without reactive contributions. Here, through explicit quantum scattering calculations, we report extensive data for rovibrational transitions in HD induced by H atoms for a range of rotational levels in v = 1 and some v = 0 levels for temperatures up to 1000 K. The significance of the computed results for astrophysical modeling is discussed.

Reactive collisions of Ca

The reactive collisions of nitrogen ion with hydrogen and its isotopic variations have great significance in the field of astrophysics. Herein, the state-to-state quantum time-dependent wave packet calculations of the N+(3P) + HD(v0 = 0, j0 = 0) → NH+/ND+ + D/H reaction are carried out based on the recently developed potential energy surface [Phys. Chem. Chem. Phys., 2019, 21, 22203]. The integral cross sections (ICSs) and rate coefficients of both channels are precisely determined at the state-to-state level. This dataset contains two Excel files, which are described below：Integral cross section.csv: the total and vibrational state-resolved ICSs (10-16 cm2) of the both products of the title reaction in the range of 0.02 - 0.4 eV.Rate coefficients.csv: the rotational state-resolved rate coefficients (cm3 s-1) of the dominant vibrational states (v' = 0) for the two products of the title reaction in the temperature range 10 - 2000K.

Water adsorption thermodynamics on a surface has attracted much attention because it may result in different configurations of water layers and modulate the properties of the surface. GaN is a typi...

Quantum time-dependent wave packet dynamics studies on the nonadiabatic Be+(2P) + HD → BeH+/BeD+ + D/H reaction are performed for the first time employing recently constructed diabatic potential energy surfaces. Strong intramolecular isotope effects and unusual results are presented, which are attributed to the dynamic effects of shallow wells induced by avoided crossing on the diagonal V22d surface. The BeH+ + D and BeD+ + H channels are dominated by high-J and low-J partial waves, respectively. The BeD+/BeH+ branching ratio is larger than 10 at low energy and gradually decreases with increasing collision energy. The BeH+ product is primarily distributed at low vibrational states, whereas there exists an obvious population inversion of vibrational states on the BeD+ product. The results of differential cross sections suggest that the formation of the BeH+ + D channel favors a direct reaction process, while the BeD+ + H channel is mainly generated by the complex-forming mechanism.

There has been increasing attention in using machine learning technologies, such as neural networks (NNs) and Gaussian process regression (GPR), to model multi-dimensional potential energy surfaces (PESs). A PES constructed using NNs features high accuracy and generalization capability, but a single NN cannot actively select training points as GPR does, resulting in expensive

Propionaldehyde is one of the most abundant aldehydes, which are an important class of volatile organic compounds. In this work, the rate coefficient of the reaction of the simplest Criegee intermediate CH2OO with propionaldehyde (CH3CH2CHO) was measured for the first time in a flash photolysis reaction tube by using the OH laser-induced fluorescence (LIF) method at temperature and pressure in the range of 283 to 318 K and 5 to 200 Torr. This reaction is observed to be pressure- and temperature-dependent. The measured rate coefficient at 50 Torr is in the vicinity of the high-pressure limit value of (3.23 ± 0.49) × 10−12 cm3 s−1 at 298 K, which is in agreement with a previously reported theoretical result of 2.44 × 10−12 cm3 s−1. The Arrhenius plot of the temperature-dependent rate coefficients yields an activation energy of (−1.99 ± 0.23) kcal mol−1.

Stimulated by the early theoretical prediction of B80 fullerene and the experimental finding of the B40 cage, the structures of medium-sized boron clusters have attracted intensive research interest during the last decade, but a complete picture of their size-dependent structural evolution remains a puzzle. Using a genetic algorithm combined with density-functional theory calculations, we have performed a systematic global search for the low-lying structures of neutral Bn clusters with n = 31-50. Diverse structural patterns, including tubular, quasi-planar, cage, core-shell, and bilayer, are demonstrated for the ground-state Bn clusters; for certain cluster sizes, unprecedented geometries are predicted for the first time. Their stabilities at finite temperatures are evaluated, and the competition mechanism between various patterns is elucidated. Chemical bonding analysis reveals that the availability of localized σ bonds and delocalized π bonds in the Bn clusters play a key role in their structural stability. Our results provide important insights into the bonding pattern and growth behavior of medium-sized boron clusters, which lay the foundation for experimental design and synthesis of boron nanostructures.

The Coherent anti-Stokes Raman scattering (CARS) microscopy is employed to characterize porous carbon materials. The slices of two dimensional (2D) CARS images are obtained, using Z-scan technology. Furthermore, the three dimensional (3D) image of CARS is reconstructed with the Z-scanned 2D CARS images. The visualizations of rotation for 3D CARS are also shown. The 2D and 3D CARS images with rotations can clearly characterize the structures and properties of porous carbon materials, including the surface and inner parts. Nonlinear optical second harmonic generation demonstrates the inversion symmetry breaking of porous carbon materials, which is not centrosymmetric material. The two-photon excitation fluorescence image reveals that porous carbon material is of weak auto-fluorescence. The clearly observed signal of two photon-excitation fluorescence provides direct evidence that photon momentum transfer to the electron system occurs. Experimental results demonstrate that the nonlinear optical microscopy is a great optical analysis method for the study of porous carbon materials, and can be potentially used for the optical characterization on the materials at micro-nano-scale.

Reaction of methanol (CH3OH) on metal surfaces has received lots of concerns because of its potential application in hydrogen (H2) production and fuel cells. In this work, we have studied the decom...

The reactive collisions of nitrogen ion with hydrogen and its isotopic variations have great significance in the field of astrophysics. Herein, the state-to-state quantum time-dependent wave packet calculations of N+(3P) + HD → NH+/ND+ + D/H reaction are carried out based on the recently developed potential energy surface [Phys. Chem. Chem. Phys. 21 22203 (2019)]. The integral cross sections (ICSs) and rate coefficients of both channels are precisely determined at the state-to-state level. The results of total ICSs and rate coefficients present a dramatic preference on the ND+ product over the NH+ product, conforming to the long-lived complex-forming mechanism. Product state-resolved ICSs indicate that both the product molecules are difficult to excite to higher vibrational states, and the ND+ product has a hotter rotational state distribution. Moreover, the integral cross sections and rate coefficients are precisely determined at the state-to-state level and insights are provided about the differences between the two channels. The present results would provide an important reference for the further experimental studies at the finer level for this interstellar chemical reaction. The datasets presented in this paper, including the ICSs and rate coefficients of the two products for the title reaction, are openly available at https://www.doi.org/10.57760/sciencedb.j00113.00034.

Two-dimensional MA2Z4 (M = Mo, W, V, Nb, Ta, Ti, Zr, Hf, or Cr; A = Si or Ge; Z = N, P, or As) is a new lead in the 2D family, because it exhibits versatile properties by tuning the components M, A and Z. However, theoretical studies on MA2Z4 are quite limited, and electronic properties are mainly studied by standard DFT levels, which seriously underestimates the band gap. Here, we systematically investigated the electronic properties and nonlinear optical response of MA2Z4 using a hybrid HSE06 functional. It was found that replacing component Z changes the lattice constant most, while the lattice influence by component M substitution is only slight. We showed that the gap difference between PBE and HSE06 is generally about 30% but can be up to 101%. (MIV = Hf, Ti, or Zr)Si2N4 possesses multi-valley characteristics. Furthermore, the second-harmonic generation (SHG) responses of various MA2Z4 composites were also calculated. Three non-zero elements of second order non-linear susceptibilities are revealed for MA2Z4 with the relationship: d16 = d21 = d22, indicating that MA2Z4 belongs to the D3H1 space group. HfSi2N4 possesses a multi-valley characteristic, and exhibits the largest susceptibility under broad wavelengths and the value of d21 reaches 3697.04 pm V-1 at band gap resonance energy. Intriguingly, the non-linear coefficients of MoSi2P4 and MoSi2As4 in the IR region are two orders of magnitude larger than those of other well-known non-linear crystals, such as LiGaS2 and BaAl4S7. We further explored the anisotropic SHG response by the polar plot of intensity under different incident light into MA2Z4. Our work provides theoretical guidelines for further experimental explorations of MA2Z4 and paves the way for its utilization in non-linear optic devices.

Using a genetic algorithm combined with density functional theory calculations, we have performed a systematic global search for the low-lying structures of 4d and 5d transition metal (M)-doped Bn clusters with n = 7–10. Diverse structural patterns have been identified as the ground state for MBn clusters, i.e., half-sandwich for early transition metal dopants, wheel-like configuration for middle transition metal dopants, quasi-planar and umbrella-like structures for late transition metal dopants. Among them, the half-sandwich RhB7, IrB7, RuB8 and OsB8; wheel-like IrB9; and umbrella-like AgB9 and AuB9 clusters have relatively high stability, which are not only stabilized by the closed-shell occupation following a circular disk Jellium model, but also enhanced by aromaticity with the π bonds distributed over the circular disk. Our results not only enrich the family of 2D superatomic clusters but also advance the fundamental understanding of the metal-doped boron clusters.

Quantum time-dependent wave packet dynamics studies on the nonadiabatic Be

Propionaldehyde is one of the most abundant aldehydes, which are an important class of volatile organic compounds. In this work, the rate coefficient of the reaction of the simplest Criegee intermediate CH2OO with propionaldehyde (CH3CH2CHO) was measured for the first time in a flash photolysis reaction tube by using the OH laser-induced fluorescence (LIF) method at temperature and pressure in the range of 283 to 318 K and 5 to 200 Torr. This reaction is observed to be pressure- and temperature-dependent. The measured rate coefficient at 50 Torr is in the vicinity of the high-pressure limit value of (3.23 ± 0.49) × 10-12 cm3 s-1 at 298 K, which is in agreement with a previously reported theoretical result of 2.44 × 10-12 cm3 s-1. The Arrhenius plot of the temperature-dependent rate coefficients yields an activation energy of (-1.99 ± 0.23) kcal mol-1.

Titanium-doped silicon clusters anions, TimSi − (m = 1‒2, n = 14‒20), have been investigated by photoelectron spectroscopy and density functional theory (DFT) calculations. Low-energy structures of TimSi − clusters have been globally searched using a genetic algorithm combined with DFT calculations. The electronic density of states and vertical detachment energies have been computed at the HSE06/aug-cc-pVDZ level and compared to the experimental data. Excellent agreement is found between theory and experiment especially in case of the singly doped clusters. In general, clusters with size m + n ≤ 17 prefer cage structures, while larger sized clusters evolve on a quasi-fullerene Ti@Si14 structural motif. Natural population analysis reveals that the Ti atoms possess negative charges and thus act as electron acceptors. The calculated binding energies and HOMO–LUMO gaps show that the clusters with cage structures have significantly higher stability, particularly Ti1Si16− and Ti2Si15−. One reason is that neutral Ti2Si15 exhibits a closed-shell electronic structure as a superatom, like Ti1Si16.

The adsorption and polymerization of acetaldehyde (CH3CHO) have been investigated on clean and CO pre-covered Co(0001) surfaces using the temperature programmed desorption (TPD) method. On the clean Co(0001) surface, CH3CHO molecules can polymerize to produce paraldehyde with very low efficiency. With pre-dosed CO molecules on Co(0001), the decomposition of CH3CHO is greatly inhibited. When the coverage of pre-dosed CO is0.33 ML, no enhancement of CH3CHO polymerization is observed. However, when the pre-dosed CO coverage is0.33 ML, the polymerization of CH3CHO is significantly enhanced during the TPD process. Further results suggest that CO molecules adsorbed at the bridge/hollow sites may initialize the polymerization by nucleophilic attack of CH3CHO molecules with their O atoms. Moreover, the polymerization product induced by CO molecules is not paraldehyde, but linear polymer chains of CH3CHO at low CH3CHO coverages and probably three dimensional polymer structures at high CH3CHO coverages.

A new accurate ab initio potential energy surface (PES) of the HeTiO system is constructed. The multi-reference configuration interaction with the Davidson correction is used to obtain the energy points, and the neural network method is employed to fit the PES. State-to-state rotational quenching cross sections and rate coefficients are obtained over a wide range based on the PES. Wigner threshold law is proved to be valid in the ultralow energy regime. In comparison with 3 He, 4 He is more efficient for the TiO molecule cooling process in the dominant transition j = 1 → 0 due to the isotope effect.

In this paper, we employ the nonlinear optical microscopies of coherent anti-Stokes Raman scattering spectroscopy, two-photon excitation fluorescence, and second harmonic generation to characterize the properties of two-dimensional (2D) materials. With these nonlinear optical microscopy methods, we can not only clearly observe the surface topography of 2D materials but also reveal the quality of 2D materials. These nonlinear optical microscopies offer great potential for characterization of the properties of 2D materials.

The kinetics of the reaction of the simplest Criegee intermediate (CH2OO) with ammonia has been measured under pseudo-first-order conditions with two different experimental methods. We investigated the rate coefficients at 283, 298, 308, and 318 K at a pressure of 50 Torr using an OH laser-induced fluorescence (LIF) method. Weak temperature dependence of the rate coefficient was observed, which is consistent with the theoretical activation energy of -0.53 kcal mol-1 predicted by quantum chemistry calculation at the QCISD(T)/CBS//B3LYP/6-311+G(2d,2p) level. At 298 K, the rate coefficient at 50 Torr from the OH LIF experiment was (5.64 ± 0.56) × 10-14 cm3 molecule-1 s-1 while at 100 Torr we obtained a slightly larger value of (8.1 ± 1.0) × 10-14 cm3 molecule-1 s-1 using the UV transient absorption method. These experimental values are within the theoretical error bars of the present as well as previous theoretical results. Our experimental results confirmed the previous conclusion that ammonia is negligible in the consumption of CH2OO in the atmosphere. We also note that CH2OO may compete with OH in the oxidation of ammonia under certain circumstances, such as at night-time, high altitude and winter time.

The Be+(2P) + H2(X1Σg+) → BeH+(X1Σ+) + H(2S) reaction has great significance for studying diabatic processes and ultracold chemistry. The first global diabatic potential energy surfaces (PESs) which are correlated with the lowest two adiabatic states 12A′ and 22A′ of the BeH2+ system are constructed by using the neural network method. Ab initio energy points are calculated using the multi-reference configuration interaction method with the Davidson correction and AVQZ basis set. The diabatic energies are obtained from the transformation of ab initio data based on the dipole moment operators. The topographical characteristics of the diabatic PESs are described in detail, and the positions of crossing between the Vd11 and Vd22 are pinpointed. On new diabatic PESs, the time-dependent quantum wave packet method is carried out to study the mechanism of the title reaction. The results of dynamics calculations indicate the reaction has no threshold and the product BeH+ is excited to high vibrational states easily. In addition, the product BeH+ tends to backward scattering at most collision energies.

The global diabatic potential energy surfaces (PESs) of the MgH2+ system, which can be used to study the dynamics of the Mg+(3p2P) + H2(X1Σ) → MgH+(X1Σ+) + H(2S) reaction, are structured for the first time. The diabatic PESs are correlated with the ground state 12A' and the first excited state 22A'. The multi-reference configuration interaction method and the VQZ basis set are used in ab initio calculations, and diabatic potential energies are calculated based on the molecular properties of the dipole moment. The neural network method is applied to fit the matrix elements of the diabatic energy surfaces. Spectroscopic constants of H2(X1Σg+) and MgH+(X1Σ+) obtained from the new PESs agree well with the experimental data. Based on the diabatic PESs of MgH2+, the time-dependent wavepacket calculations for the Mg+(3p2P) + H2(X1Σg+) → MgH+(X1Σ+) + H(2S) reaction are carried out to study the reaction dynamics. There is no threshold for this reaction because of the existence of barrierless reactive paths. The reaction has a high total integral cross section (ICS), and vibrationally resolved ICSs show an obvious population inversion of product vibrational states. The results of differential cross sections (DCSs) indicate that most product molecules tend to forward scatter.

Non-adiabatic quantum dynamics study of the Mg+(3p) + D2 reaction was carried out by using the time-dependent wave packet method. The results show that there is the triatomic complex supported by the well along the reaction path, which is manifested as metastable resonances on the probability curves. The MgD+ products are obtained via a non-adiabatic pathway, and the reaction is more efficient than the quenching progress at the selected collision energies. The product angular distributions present obvious forward scattering bias, and the weak backward scatterings are mainly contributed by the new partial waves that are opened as the collision energy increases. Further rovibrational state-resolved results reflect that the predominant forward scattering correlates with the internally hot products and the backward-scattered products occupy the colder vibrational and rotational states.

In this paper, different sizes of Ag nanoparticles grown on TiO 2 film have been fabricated using UV-photoreduction method and studied by UV–vis absorption spectroscopy, ultrafast transient absorption spectroscopy and surface-enhanced Raman scattering (SERS) spectroscopy. The results demonstrated that the plasmon-exciton coupling degree can be well manipulated by changing Ag nanoparticle size, because the surface plasmon resonance (SPR) peak can be controlled by Ag nanoparticle size. The strongest plasmon-exciton coupling occurred when the SPR peak of Ag nanoparticles superposed with the absorption peak of exciton of TiO 2 film, which is the optimal catalytic platform for surface catalytic reactions. Our findings might promote a deeper understanding of the reaction mechanism for plasmon-exciton co-driven surface catalytic reactions.

The non-adiabatic state-to-state dynamics of the Li(2p) + H2 → LiH + H reaction has been studied using the time-dependent wave packet method, based on a set of diabatic potential energy surfaces recently developed by our group. Integral cross sections (ICSs) can be increase more than an order of magnitude by the vibrational excitation of H2, whereas the ICSs are barely affected by the rotational excitation of H2. Moreover, ICSs of the title reaction with vibrationally excited H2 decrease rapidly with increasing collision energy, which is a typical feature of non-threshold reaction. This phenomenon implies that the title reaction can transformed from an endothermic to an exothermic reaction by vibrational excitation of H2. With the increase of the collision energy, the sideways and backward scattered tendencies of LiH for the Li(2p) + H2(v = 0, j = 0, 1) → LiH + H reactions are enhanced slightly, while the backward scattering tendency of LiH for the Li(2p) + H2(v = 1, j = 0) → LiH + H reaction becomes remarkably weakened. For the reaction with vibrationally excited H2 molecule, both direct and indirect reaction mechanism exist simultaneously.

The time-dependent wave packet quantum dynamics studies for the Mg+(3p) + HD → MgH+/MgD+ + D/H diabatic reaction are carried out for the first time on recently developed diabatic YHWCH potential energy surfaces [Phys. Chem. Chem. Phys., 2018, 20, 6638–6647]. The results of reaction probabilities and total integral cross sections show a dramatic preference to the formation of MgD+ over MgH+ owing to the insertion reaction mechanism in the title reaction. The MgD+/MgH+ branching ratio witnesses a monotonic decrease from 10.58 to 3.88 at collision energy range of 0.01 to 0.20 eV, and at the collision energy of 0.114 eV, it is close to the experimental value of 5. The rovibrational state-resolved ICSs of the two channels show the products MgD+ have higher vibrational excitation and hotter rotational state distributions. The opacity function P(J) suggests that the MgH+ + D channel and MgD+ + H channel are dominated by high-b and low-b collisions, respectively. Both forward and backward scattering peaks are found in the differential cross section curves, whereas the angle distributions of products are not strictly forward-backward symmetric because of the short lifetime of the complex in the reaction.

Time-dependent wave packet calculations are carried out for two reaction channels of the non-adiabatic Na(3p) + HD → NaH/NaD + D/H reaction. The potential well on the excited state potential energy surface makes the reaction preferable to proceed through the insertion reaction path. The dominance of the NaD + H reaction channel and product rotational state distributions are found to be in agreement with the characteristics of typical adiabatic insertion reactions. However, significant forward scattering peaks in the differential cross sections (DCS) are found to be inconsistent with the forward-backward symmetric scattering characteristic of typical adiabatic insertion reactions, which indicate that the Na(3p) + HD reaction is dominated by a direct reaction mechanism. The comparison between adiabatic and non-adiabatic calculated DCSs reveals that the non-adiabatic couplings in the reaction could reduce the lifetime of the intermediate complex. Finally, the insertion–abstraction mechanism is put forward for the non-adiabatic Na(3p) + HD reaction.

Using nonlinear optical microscopy of coherent antistokes Raman scattering (CARS), second harmonic generation (SHG) and two-photo excitation fluorescence, we in situ observed how the collagen and the bone grow synergistically and competitively during nascent biological evolution. The sds CO 3 2 - and PO 3 2 - ions were first observed to be dispersed in the liquid environment, and the collagen was observed 2 days later. With the help of the collagen, the CO 3 2 - and PO 3 2 - ions gradually moved closer to the collagen, and then the bone was produced in the forms of CaCO3 and CaPO3 . When the bone was completed with the help of the collagen, the collagen gradually disappeared. The biological evolution of snail bone and collagen can be well revealed by CARS and SHG, and in addition, the biological evolution of structure and morphology can be clearly observed day by day.

Plasmon-driven diazo coupling reaction of p-nitroaniline (PNA), containing both an amine group (−NH2) and a nitro group (−NO2), in ambient atmosphere environments remains unknown in experiments, on both metal nanoparticles and graphene-mediated metal nanostructures. Using the surface-enhanced Raman scattering (SERS) technique, we presented the surface coupling reactions of PNA under atmospheric environment, adsorbed on the Ag nanoparticle (AgNP) arrays, graphene-coated Ag nanoparticle (G/AgNPs) hybrids, and graphene-covered Ag nanowire (G/AgNW) composites, respectively. It was found that PNAs were converted into 4,4′-diaminoazobenzene (DAAB) through a selective reduction reaction, rather than oxidized into 4,4′-dinitroazobenzene (DNAB). These results may be useful for understanding the reaction mechanism for plasmon-driven chemical reactions of the molecules containing both amine groups and nitro groups under ambient conditions.

In this work, charge-transfer mechanism of surface-enhanced resonance Raman scattering (SERRS) spectroscopy of pyrazine absorbed on Ac@Au7 clusters is theoretically investigated, and the coupling effect between the nanoparticles is especially concerned. First, the contributions of coupling effect to surface-enhanced Raman scattering (SERS) are compared between the ground-state nanoparticles. Second, the visualization of charge transfer provides evidence for the coupling effect on the charge-transfer enhancement mechanism of SERRS spectroscopy. The theoretical results show that the coupling effect on charge-transfer mechanism of SERRS can significantly enhance the intensity of SERS spectra up to about 6 × 105 times. The different coupling ways not only result in different degree of charge transfer on electronic transitions, but also cause different intensity of charge-transfer absorption peaks. Both of them strongly influence the enhancement of charge-transfer mechanism of SERRS. This study promotes the understanding of charge-transfer enhancement mechanism of SERRS for ultrasensitive Raman spectral analysis at nanoscale. Copyright © 2017 John Wiley & Sons, Ltd.

In order to study the dynamics of the reaction H(2S) + NaH(X1Σ+) → Na(2S) + H2(X1Σg+), a new potential energy surface (PES) for the ground state of the NaH2 system is constructed based on 35 730 ab initio energy points. Using basis sets of quadruple zeta quality, multireference configuration interaction calculations with Davidson correction were carried out to obtain the ab initio energy points. The neural network method is used to fit the PES, and the root mean square error is very small (0.00639 eV). The bond lengths, dissociation energies, zero-point energies and spectroscopic constants of H2(X1Σg+) and NaH(X1Σ+) obtained on the new NaH2 PES are in good agreement with the experiment data. On the new PES, the reactant coordinate-based time-dependent wave packet method is applied to study the reaction dynamics of H(2S) + NaH(X1Σ+) → Na(2S) + H2(X1Σg+), and the reaction probabilities, integral cross-sections (ICSs) and differential cross-sections (DCSs) are obtained. There is no threshold in the reaction due to the absence of an energy barrier on the minimum energy path. When the collision energy increases, the ICSs decrease from a high value at low collision energy. The DCS results show that the angular distribution of the product molecules tends to the forward direction. Compared with the LiH2 system, the NaH2 system has a larger mass and the PES has a larger well at the H-NaH configuration, which leads to a higher ICS value in the H(2S) + NaH(X1Σ+) → Na(2S) + H2(X1Σg+) reaction. Because the H(2S) + NaH(X1Σ+) → Na(2S) + H2(X1Σg+) reaction releases more energy, the product molecules can be excited to a higher vibrational state.

The dynamic properties of the title reaction calculated by classical and quantum methods show large deviations from each other, whereas for the barrierless and exothermal reaction two methods should show good agreement. In order to further investigate the reaction mechanism of the title reaction, a global PES for the electronic ground state was constructed. The energy points are calculated by the multireference configuration interaction method with aug-cc-pVQZ and cc-pwCVQZ basis sets for H and Li atoms, respectively. The neural network approach is adopted in the fitting process. The classical and quantum methods are applied in the dynamic calculation based on the new PES. As expected, the dynamic properties obtained by these two methods are in good agreement with each other. In addition, two reaction mechanisms were found. When the energy is below 0.2 eV the insert reaction mechanism is dominant, and this changes to the abstract reaction mechanism as the energy increases.

In this study, we theoretically investigated the Raman and absorption spectra of pyrazine adsorbed on Au5Al5 bimetallic nanoclusters by a time-dependent density functional theory (TD-DFT) method. The surface-enhanced resonance Raman scattering (SERRS) spectra of pyrazine absorbed on different isomers and sites of the Au5Al5 cluster were simulated. The visualization of orbital transitions in electronic transitions was used to analyze the enhancement mechanism of SERRS spectroscopy. Compared with those of isolated pyrazine excited at 598 nm, the SERRS of pyrazine–Au–Au4Al5-a excited at the same incident light can be enhanced on the order of 104, which is a typical charge transfer (CT) resonance excitation and charge transfer from substrate to pyrazine. Due to the fact that the intensity of ultraviolet SERRS can be significantly enhanced to 1.2 × 106 A4 per amu for pyrazine–Au–Au4Al5-a model at 280 nm, the Au5Al5 cluster may be a good candidate for research of the ultraviolet SERRS materials. Other key factors that can change the intensity of SERRS include the resonance excitation wavelength, oscillator strength of the electronic excited state, metal–molecule binding site and structure of the substrate cluster. Hence, the optical properties of complexes can be tuned by varying these factors.