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The mechanism of exchange reactions CO(X1Σ+) + N(4S) ↔ CN(X2Σ+) + O(3P), CO(X1Σ+) + N(4S) ↔ NO(X2Π) + C(3P), CN(X2Σ+) + O(3P) ↔ NO(X2Π) + C(3P) occurring under the conditions of entry into the Mars atmosphere was investigated on the basis of DFT modeling 4A'' potential energy surface. Reaction paths, transition states, intermediate complexes and the corresponding vibration frequencies and energy characteristics were found via calculation of the potential energy surface for the system under consideration. It is shown that the mechanisms of all reactions are multistage, and pass through the formation of several sequential intermediate complexes. The rate constants of the studied reactions were calculated in a wide range of temperatures and compared with the available experimental data.

Quantum state-to-state dynamics calculations are reported for the H + LiF(vi, ji) → HF(vf, jf) + Li reaction on a recently reported ground state X 2 A ′ potential energy surface. It was found that at low collision energies the title reaction is dominated by long-lived resonances, while the lifetimes of resonances become shorter at higher energies. The existence of resonances is also supported by the differential cross section, which has mostly forward and sideways bias. The integral cross section rises with collision energy slowly, and the opacity function suggests that the reaction is dominated by small impact parameter collisions. The HF product has cold vibrational state distributions in range of the collision energy studied here, although its rotational state distributions peak near the highest accessible rotational states. This early-barrier reaction shows some enhancement by translational energy, but internal excitations of the LiF reactant have more complex behaviors.

The ro-vibrational transitions of NaH are crucially needed for the control of photo-association processes resulting from its formation and for accurately modeling the NaH abundance in space. In this work, we constructed new PESs of the NaH-He system. The potentials were computed at the CCSD(T)-F12/ cc-pVTZ level of theory. Each of the PESs presents two local minima. From these PESs, we calculated rotational cross sections of NaH induced by collision with He using the close coupling approach. These cross sections were then averaged at low temperature to obtain the collisional rates. The propensity rules favorite odd Δ j transitions. The collisional rates presented in this paper may be crucial for the astrophysical community. The three dimensional PES can be used later to compute ro-vibrational quenching rate coefficients to interpret the NaH collisional interaction with laser-cooled atoms.

To study the dynamics resonances of the Cl + HD reaction which was proposed to proceed via abstraction mechanism with no clear resonances, we perform dynamics calculations by the multiconfiguration time-dependent Hartree (MCTDH) method based on recently developed neural-networks potential energy surface (Science 347 (2015), 60). The HD molecule in v = 0 (GS), v = 1 (EX1), v = 2 (EX2), and v = 3 (EX3) states is used for the reactant. For GS, no distinctive resonance peak is found, while for EX1 two distinctive peaks at kinetics energies of 0.11 and 0.17 eV are investigated. These resonance peaks are well consistent with the previous results (Science 347 (2015), 60). Moreover, the present MCTDH calculations predict well-marked resonance peaks at 0.04 , 0.05 , 0.07 , and 0.10 eV for EX2 and EX3, which indicates that anticipation of the chemical bond softening model (Science 327 (2010), 1501) is confirmed in this work.

A new global potential energy surface (PES) for the ground ( X 2 A ′ ) state of the Li + HF → LiF + H reactive system is constructed by fitting 12,399 points computed at the UCCSD(T)-F12b/aug-cc-pV5Z level of theory. The use of a neural network method helps to achieve a high-fidelity fit with a root mean square error of 0.88 meV. Quantum dynamics calculations with full Coriolis coupling on the new PES yield both differential and integral cross sections over a range of energy. In agreement with experiment, the product angular distribution depends sensitively on collision energy, but all with a forward bias. Moderate internal excitation is found in the LiF product. The energy dependence of the integral cross section is in reasonably good accord with the experimental excitation function, although some quantitative differences persist. This late-barrier reaction shows a dramatic vibrational enhancement of reactivity. The mode specificity is rationalized using the Sudden Vector Projection model.

A new potential energy surface (PES) of the ground state (X2A′) of Li2H was built using 18,403 ab initio points. The MRCI-F12 method with AVQZ basis set were used in the ab initio calculation. Furthermore, the widely used permutation invariant polynomial neural network method was adopted in the fitting process. The features of new PES were compared with previous theoretical and experimental studies. The results indicated that the spectroscopic parameters of PES are in good agreement with experimental data. In addition, the dynamics calculations of the H + Li2 → Li + LiH reaction were carried out using time-dependent wave packet method based on the new PES. The dynamics properties such as reaction probability, integral cross section and thermal rate constant were reported and compared with previous theoretical studies.

The paper studies the potential energy surface (PES) of interaction between two rigid diatomic molecules (N2–N2, N2–O2, O2–O2). The dependence of energy on the angles of mutual orientation of the two molecules is carefully described (18000 DFT calculations for each pair) so that the obtained PES would be suitable for detailed simulation of the rotational excitation and relaxation in intermolecular collisions in air. The DFT results were fitted by proposed multi-particle interaction model with good accuracy. Corresponding force field was calculated and tested on two problems (simulation of the equilibrium state and the adiabatic rotational relaxation), its software implementation is attached to the paper and one can use it for molecular dynamics calculations.

Binding energy (BE) is an important descriptor in chemistry, which determines thermodynamics and phase behavior of a given substance. BE between two molecules is not directly accessible from the experiment. It has to be reconstructed from cohesive energies, vaporization heats, etc. We report BE for the excited states of two semiconductor molecules – boron-dipyrromethene (BODIPY) and graphene quantum dot (GQD) – with water. We show, for the first time, that excitation increases BE twofold at an optimal separation (energy minimum position), whereas higher separations lead to higher differences. Interestingly, the effects of excitation are similar irrespective of the dominant binding interactions (van der Waals or electrostatic) in the complex. This new knowledge is important for simulations of the excited semiconductors by simplified interaction functions.

The intermolecular potential energy surface (PES) of the ground electronic state for the Ar-BrCl dimer is constructed at the CCSD(T) level with the aug-cc-pVQZ basis set and mid-bond functions. The PES is characterized by three minima and two saddle points. The global minimum corresponding to a collinear Ar-BrCl configuration, which has been observed experimentally, is located at R = 4.10 angstrom and theta = 2.5 degrees with a well depth of -285.207 cm (1). A nearly T-shaped structure and an anti-linear Ar-ClBr geometry is also predicted. The bound state calculations are preformed to study intermolecular vibrational modes, rotational levels and average structures for the complex. Our transition frequencies, spectroscopic constants and average structures for all isotopomers of the collinear isomer agree well with experimental data. We have also provided pure rotational transitional frequencies for both nearly T-shaped and anti-linear isomers. These results are significant for further experimental investigations of the Ar-BrCl dimer. (C) 2015 Elsevier B.V. All rights reserved.