Dynamics studies of O+ + D2 reaction using the time-dependent wave packet method

Based on the potential energy surface (PES) reported by Li et al. (Phys. Chem. Chem. Phys. 20, 1039 (2018)), the initial state dynamics calculation of O⁺?+?D₂ (v?=?0, j?=?0) reaction was conducted using the time-dependent wave packet method with a second order split operator. Dynamics properties such as reaction probability, integral cross section, differential cross section, and distribution of products were calculated and compared with available experimental and theoretical results. The present integral cross section values were in good agreement with experimental results. In addition, the differential cross section indicates that the mechanism of the complex-formation reaction plays a dominant role during the reaction.     

A quantum wave packet study of three-dimensional inelastic scattering: He—H2

A time-dependent quantum mechanical method has been described to calculate the state-to-state inelastic scattering probabilities for three-dimensional atom—diatom inelastic scattering at the zero total angular momentum. The method utilizes the potentially optimized discrete variable representation (DVR) technique for operating a diatomic Hamiltonian on the wave function and avoids the necessity of repeating many Fourier transformations for this operation. The method has been applied to the He + H₂(v,j)→ He + H₂(v′,j′) inelastic scattering problem.     

State-to-state quantum dynamics studies of the H + LiH+ → Li+ + H2 reaction

ABSTRACT

Quantum dynamical calculations of the H?+?LiH⁺?→?Li⁺?+?H₂ reaction were performed based on the potential energy surface (PES) reported by Dong et al. (RSC Adv. 7, 7008 (2017)) using the time-dependent quantum wave packet method in collision energy range from 0.01 to 1.0?eV. Dynamics properties such as reaction probability, integral cross section, differential cross section (DCS), and thermal rate constant of the H?+?LiH⁺?→?Li⁺?+?H₂ reaction were reported at the state-to-state level of theory and compared with available theoretical calculations. The results indicated that present values are in good agreement with results obtained from the quasi-classical trajectory method. However, large differences can be found between present values and previous quantum results. This can be attributed to the different PESs used in the calculation and the CS approximation was adopted in previous theoretical studies. In addition, the ‘rebound’ reaction mechanism was proposed in previous theoretical studies in a high collision energy range. However, the DCS scattering signals calculated in the present work indicated that complex-forming and direct abstract reaction mechanisms are dominant in low and high collision energies, respectively.     

Scattered wave packet formalism for open quantum systems: Comparison with the non-Markovian time-dependent Schrödinger equation

Computational comparison is presented between the scattered wave packet formalism and the non-Markovian time-dependent Schrödinger equation (TDSE). These two approaches have been developed to deal with open quantum systems. We employ these methods to study the dynamics of a Gaussian wave packet scattering from the Eckart barrier. It is shown that strongly oscillatory Green functions required in the integration of the non-Markovian TDSE significantly increase computational effort even for one-dimensional problems. Computational results indicate that the scattered wave packet formalism can achieve higher accuracy and can be several orders of magnitude faster than the integration of the non-Markovian TDSE.     

Effect of (H2O)n (n = 1–3) clusters on H2O2 + HO → HO2 + H2O reaction in tropospheric conditions: competition between one-step and stepwise routes

ABSTRACT

Effects of (H₂O)_n (n?=?1–3) on the H₂O₂?+?HO?→?HO₂?+?H₂O reaction have been investigated by the reactions of H₂O₂L(H₂O)_n (n?=?1–3)?+?HO and H₂O₂?+?HOL(H₂O)_n (n?=?1–3) at the CCSD(T)/CBS//M06-2X/aug-cc-pVTZ level of theory, coupled with rate constant calculations by using canonical variational transition state theory. Interestingly, for the former reactions, one-step process and stepwise mechanism are involved, where one-step processes occurring though cage-like hydrogen bonding network complexes and the transition states are favourable. Due to larger effective rate constants, these favourable processes are also favourable than the corresponding latter reactions. Meanwhile, the catalytic effect of (H₂O)_n (n?=?1–3) is mainly taken from water monomer, because the effective rate constant (k'(R_WM2)) of H₂O₂···H₂O?+?HO reaction is, respectively, larger by 3, 6–10 orders of magnitude than that of H₂O₂···(H₂O)₂?+?HO (k'(R_WD1)) and H₂O₂···(H₂O)₃?+?HO (k'(R_WT1)) reactions. Furthermore, the enhancement factor of water molecular (k'(R_WM2)/k_tot) is only 0.28% at 240?K, while at high temperature (such as at 425?K), the positive water vapour effect enhances up to 27.13%. This shows that at high temperatures the positive water effect is obvious under atmospheric conditions.     

Time-dependent quantum wave packet and quasiclassical trajectory studies of the Au(2S) + H2(X1∑+g) → AuH(X1∑+g) + H(2S) reaction

The time-dependent quantum wave packet (TDWP) and quasiclassical trajectory calculations (QCT) are carried out for the Au(²S) + H₂(X¹∑⁺_g) → AuH(X¹∑⁺_g) + H(²S) reaction on a global potential energy surface. The reaction probabilities at a series of J values, integral cross sections (ICSs) and differential cross sections of the title reaction are calculated by the TDWP method. For reaction probabilities, there are a mass of sharp oscillations at low collision energy, which can be attributed to resonances supported by the potential well. Due to the endothermicity of the title reaction, the total ICS shows a threshold about 1.53 eV. In order to further investigate the reactive mechanism, the lifetime of complex is calculated by QCT method. At the low collision energy, most intermediate complexes are long lived, which implies that the reaction is governed by indirect reactive mechanism. With the collision energy increasing, the direct reactive mechanism occupies the dominant position. Due to the change of the reactive mechanism, the angular distribution shifts toward the forward direction with collision energy increasing. The isotopic variant, Au + D₂→AuD + D reaction, is also calculated by TDWP method. The calculated reaction probabilities and ICSs show that the isotope effect reduces the reactivity.     

Dynamical studies and product analysis of O(1D) + H2/D2 reactions

The aim of this study was to analyse the dynamics of O(¹D)?+?H₂/D₂ reactions using quasiclassical trajectory calculations on a double-valued potential energy surface for H₂O. Produced on the photodissociation of stratospheric ozone, the excited oxygen atom is a highly reactive species whose chemistry plays a key role in the ozone depletion cycle. In order to make comparisons with experiment, we studied these reactions at fixed translational collision energies. In particular, we consider the reactive cross sections, the thermal rate constants, the opacity function, and the differential cross sections. In addition, we also study the energy distribution of the products and compare the results with experiment and calculations based on phase space statistical theory. Results for the rotational population of the OH products are also compared with experimental results. The agreement between our results and experiment reinforces the accuracy of the H₂O potential energy surface used.     

State-to-state dynamics of reactions H+DH'(v=0,j=0)→HH'(v',j')+D/HD(v',j')+H'with time-dependent quantum wave packet method

State-to-state time-dependent quantum dynamics calculations have been carried out to study H+DH'→HH'+D/HD+H' reactions on BKMP2 surface.The total integral cross sections of both reactions are in good agreement with earlier theoretical and experimental results,moreover the rotational state-resolved reaction cross sections of H+DH'→HH‘+D at collision energy Ec=0.5 eV are closer to the experimental values than the ones calculated by Chao et al [J.Chem.Phys.117 8341(2002)],which proves the higher precision of the quantum calculation in this work.In addition,the state-to-state dynamics of H+DH'→ HD'+H reaction channel have been discussed in detail,and the differences of the micro-mechanism of the two reaction channels have been revealed and analyzed clearly.     

State-to-state quantum dynamics of the N(~4S)+H_2(X~1Σ~+) → NH(X~3Σ~-)+H(~2S) reaction and its reaction mechanism analysis

Quantum state-to-state dynamics of the N(4S) + H-2(X1+Σ) → NH(X3Σ) + H(2S) reaction is reported in an accurate novel potential energy surface constructed by Zhai et al.(2011 J. Chem. Phys. 135 104314). The time-dependent wave packet method, which is implemented on graphics processing units, is used to calculate the differential cross sections. The influences of the collision energy on the product state-resolved integral cross sections and total differential cross sections are calculated and discussed. It is found that the products NH are predominated by the backward scattering due to the small impact parameter collisions, with only minor components being forward and sideways scattered, and have an inverted rotational distribution and no inversion in vibrational distributions; both rebound and stripping mechanisms exist in the case of high collision energies.     

Stereodynamics study of reactions N(~2D)+HD→NH+D and ND+H

The product polarizations of the title reactions are investigated by employing the quasi-classical trajectory (QCT) method. The four generalized polarization-dependent differential cross-sections (PDDCSs) $({2\pi } / \sigma )(\d\sigma _{00} / \d\omega _t )$, $({2\pi } / \sigma )(\d\sigma _{20} / \d\omega _t )$, $({2\pi } / \sigma )(\d\sigma _{22 + } / \d\omega _t )$, and $({2\pi } / \sigma )(\d\sigma _{21 - } / \d\omega _t )$ are calculated in the centre-of-mass frame. The distribution of the angle between ${{\bm k}}$ and ${{\bm j^\prime }}$, $P(\theta _r )$, the distribution of the dihedral angle denoting ${{\bm k}}${--}$\bm k^\prime $--$\bm j^\prime $ correlation, $P(\phi _r )$, as well as the angular distribution of product rotational vectors in the form of polar plots $P(\theta _r ,\phi _r )$ are calculated. The isotope effect is also revealed and primarily attributed to the difference in mass factor between the two title reactions.     

State-to-state integral cross sections and rate constants for the N+(3P)+HD→NH+/ND++D/H reaction: Accurate quantum dynamics studies

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$^{+}$($^{3}$P)$+{rm HD}to {rm NH}^{+}$/ND$^{+} +{rm D/H}$ 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.     

Vibrational and rotational excitation effects of the N(2D) + D2(X1Σg +) → ND(X3Σ+) + D(2S) reaction

The effects of the rovibrational excitation of reactants in the N(²D) + D₂(X¹Σ_g⁺) → ND(X³Σ⁺) + D(²S) reaction are calculated in a collision energy range from the threshold to 1.0 eV using the time-dependent wave packet approach and a second-order split operator. The reaction probability, integral cross-section, differential cross-section and rate constant of the title reaction are calculated. The integral cross-section and rate constant of the initial states v = 0, j = 0, 1, are in good agreement with experimental data available in the literature. The rotational excitation of the D₂ molecule has little effect on reaction probability, integral cross-section and the rate constant, but it increased the sideways and forward scattering signals. The vibrational excitation of the D₂ molecule reduced the threshold and broke up the forward–backward symmetry of the differential cross-section; it also increased the forward scattering signals. This may be because the vibrational excitation of the D₂ molecule reduced the lifetime of the intermediate complex.     

Inversion doubling in the ν2 vibration-rotation band of NH2D and ND2H

This paper is concerned with an analysis of both ¹⁴NH₂D and ¹⁴ND₂H spectra obtained in the 730- to 1080-cm⁻¹ region with a long-path Fourier transform spectrometer. The assignment of the observed transitions together with a theoretical analysis of the vibration-inversion-rotation energy levels concerned with these transitions allows the first determination of the spectroscopic constants related to the symmetric and antisymmetric upper levels of the fundamental ν₂ band.     

Ab initio dynamics of the He + H+ 2 → HeH+ +H reaction: a new potential energy surface and quantum mechanical cross-sections

The reaction He + H⁺ ₂(v,j = 0) → HeH⁺(v′ = 0, j′) for v = 0, 1,2 and 3 and for scattering energies near the threshold (0.95–1.15 eV) has been studied by calculating ab initio points at MRCI level and ‘exact’ integral quantum reactive cross-sections. More than 1400 nuclear geometries have been chosen to cover the most important regions for the dynamics, an extended set of points being taken directly on a hyperspherical coordinate grid. A many-body expansion with a large number of terms permits an accurate analytical representation of the potential energy surface with a root-mean-square deviation <12meV. The hyperquantization algorithm has been extended to obtain quantum mechanical integral cross-sections which are compared with previous calculations and with experimental results.     

Direct mapping of insertion reaction dynamics: S(1D)+H2→SH+H

The Doppler-selected time-of-flight method was applied to map out the differential cross sections of the title reaction at two collision energies in a crossed-beam experiment. Roughly symmetric and highly forward–backward peaking angular distributions were observed at both energies. Vibrational structures of the SH product were resolved from the velocity measurements of the counter-product H-atom. Most of the angle-integrated observables can readily be understood on statistical grounds, which suggests that statistics plays the dominant role in determining the outcomes of this prototypical insertion reaction. In terms of more detailed angle-specific reaction attributes, significant discrepancies from statistical considerations were revealed, indicative of some hidden dynamics being buried under the statistical factor. Received: 26 February 2000 / Revised version: 20 April 2000 / Published online: 13 September 2000     

Ab initio investigation of the gas phase reaction SO2 + H2O → SO2OH radical

High level ab initio calculations have been performed to investigate the reaction of the OH radical with SO₂. This reaction has been suggested as a possible first step in the atmospheric oxidation of SO₂. Results from both density functional theory (DFT) and second-order M?ller-Plesset calculations are reported. A small barrier has been located in the reaction channel and the structure of the corresponding transition state characterized. On the potential energy surface, the product, HOSO₂, occupies a double well potential that corresponds to a pair of equal energy rotamers separated by a barrier of ～12 kJ mol^?1 corresponding to a symmetric transition state.     

Energy and rotation-dependent stereodynamics of H(~2S) + NH(a~1?) → H_2(X~1Σ_g~+) + N(~2D) reaction

Quasi-classical trajectory calculations are performed to study the stereodynamics of the H(~2S) + NH(a~1?) →H_2(X~1Σ_g~+) + N(~2D) reaction based on the first excited state NH_2(1~2A') potential energy surface reported by Li et al.[Li Y Q and Varandas A J C 2010 J. Phys. Chem. A 114 9644] for the first time. We observe the changes of differential cross-sections at different collision energies and different initial reagent rotational excitations. The influence of collision energy on the k–k' distribution can be attributed to a purely impulsive effect. Initial reagent rotational excitation transforms the reaction mechanism from insertion to abstraction. The effect of initial reagent rotational excitations on k–k' distribution can be explained by the rotational excitation enlarging the rotational rate of reagent NH in the entrance channel to reduce the probability of collision between incidence H atom and H atom of target molecular. We also investigate the changes of vector correlations and find that the rotational angular momentum vector j' of the product H_2 is not only aligned, but also oriented along the y axis. The alignment parameter, the disposal of total angular momentum and the reaction mechanism are all analyzed carefully to explain the polarization behavior of the product rotational angular moment.     

STM investigation of the reaction of AgO added rows with CO2 on a Ag(110) surface

The formation of carbonate species by a reaction of AgO added rows with CO₂ was investigated by scanning tunneling microscopy (STM). STM observation during the reaction revealed that the AgO added rows were compressed from a (4 × 1) to a (2 × 1) phase, according to the growth of carbonate domains. Though the carbonate domains give a (1 × 2) diffraction pattern, STM images of this domain do not show a (1 × 2) structure, which indicates that the Ag substrate reconstructs to a (1 × 2) structure. Though the CO₃ species thermally decompose at a lower temperature than AgO added rows, the AgO added rows can be selectively decomposed by ultraviolet irradiation.