Rate coefficients for C and O2 reactive collisions relevant to interstellar clouds from QCT and machine learning.

The chemical reactions between certain interstellar molecules are exothermic in nature and barrierless in the entrance channel, allowing these reactions to occur rapidly even at low astronomical temperatures, e.g., C and O2 interaction.

Exhaustive State-to-State Cross Sections and Rate Coefficients for Inelastic N-N Collisions using QCT Combined with Neural Network Models.

Using the quasi-classical trajectory method, we systematically studied the state-to-state vibrational relaxation process of N() + N() collisions over a wide temperature range (5000-30,000 K). Different temperature dependencies of the single- and multiquantum VV and VT events in various (,) collisions are captured, with the dominant channel being related to the initial vibrational energy levels ( = 50). At a specified relative translational energy, there is a monotonic relationship of the VT cross sections with the vibrational energy level, particularly in high-energy collisions.

Dissociation cross sections and rates in O + N collisions: molecular dynamics simulations combined with machine learning.

The collision-induced dissociation reaction of O (, ) + N, a fundamental process in nonequilibrium air flows around reentry vehicles, has been studied systematically by applying molecular dynamics simulations on the ', ' and ' potential energy surfaces of NO in a wide temperature range. In particular, we have directly investigated the role of the ' surface in this process and discussed the applicability of the simplified approximate rate models proposed by Esposito and Andrienko based on the lowest two surfaces. The present work indicates that the state-selected dissociation of O + N is dominated by the ' surface for all except for the low-lying O states.

Exhaustive state-specific dissociation study of the N2(Σg+1)+N(S4) system using QCT combined with a neural network method.

This work studies the exhaustive rovibrational state-specific collision-induced dissociation properties of the N2+N system by QCT (quasi-classical trajectory) combined with a neural network method based on the ab initio PES recently published by Varga et al. [Phys. Chem.

Real-time dynamic simulation of laser-induced N dissociation on two-dimensional graphene sheets.

Due to its relatively high inertness, nitrogen dissociation at ambient temperature and pressure has always been a challenging task. Plasmon driven photocatalysis has proved to be an effective method. Owing to their unique physical, chemical, and electronic properties, two-dimensional planar materials have become the most promising candidates to replace noble metal catalytic nitrogen reduction.

The role of the sextet potential energy surface in O + N inelastic collision processes.

We have performed molecular dynamics simulations of inelastic collisions between molecular oxygen and atomic nitrogen, employing the quasi-classical trajectory method on the new doublet, quartet, and sextet analytical potential energy surfaces of NO. A complete database of vibrationally detailed rate coefficients is constructed in a wide temperature range for high vibrational states up to = 25. In particular, the present work shows that the sextet potential energy surface plays a crucial role in the rovibrational relaxation process of O + N collisions.

-Matrix Calculation of Electron Collisions with Molecular Oxygen in Its Electronically Excited States.

Low-energy electron collisions with the XΣ- ground state and aΔ and bΣ+, the Herzberg states (cΣ, A'Δ, and AΣ+), and BΣ excited states of the O molecules are studied using the fixed-nucleus -matrix method. Integral elastic scattering and electronic excitation cross sections from the XΣ ground state overall agree well with the available experimental and theoretical results. The electronic (de-)excitation cross sections for the electron impact with the Herzberg states and the BΣ state are reported.

Separation of C/C binary organic gas mixtures via flexible nanoporous carbon molecular sieves: DFT calculations and MD simulations.

The C/C hydrocarbon gas separation characteristics of nanoporous carbon molecular sieves (CMS) are studied using DFT calculations and MD simulations. To efficiently separate the equimolar CH/CH and CH/CH gas mixtures, CNT gas transport channels are embed between the polyphenylene membranes which created structural deformation for both CNT and membrane. The adsorption and permeation of gas molecules via CMS and the effect of nanochannel density and electric field on gas selectivity are analyzed.

Study on the Ti K, L, and M Edges of SrTiO and PbTiO.

The multiplet theory of free ions combined with crystal field theory is used to study core electron excitation of perovskites. This combined method is helpful to further identify transition peaks and comprehend the transition mechanism. In this paper, the core electron excitation of Ti K edge, L edges, and M edge in SrTiO and PbTiO is studied, and the identification of peak and the analysis of spectral shape are emphasized.

Kohn anomaly and van Hove singularity in IV and V group transition metals nitrides and carbides.

The superconducting behavior in IVB-VB group transition metal nitrides and carbides has generally been associated with the phonon anomaly and Fermi surface nesting. However, the origin of phonon anomaly has remained ambiguous (i.e.

MD simulation of methane adsorption properties on pillared graphene bubble models.

Pillared graphene bubble framework is selected as the methane storage vessel in this article. All investigations of methane adsorption are executed by using the MD simulations. The average adsorption energy of methane on different bubble models is between - 4.

Simulations on methane uptake in tunable pillared porous graphene hybrid architectures.

In this article, 3D pillared carbon nanotube (CNT)-porous graphene (PG) nanomesh architectures are computationally investigated as methane storage nanocontainer. The purpose of this article is to screen the configurations of 3D pillared CNT-PG materials and to select the optimal one for maximizing the methane storage capacity. Molecular mechanics (MM) calculations and MD simulations are executed to depict the structural characteristics and methane adsorption properties.

Theoretical studies of some bimolecular reactions during the decomposition of CHNO: reactions between NO and nine intermediates.

Nitromethane (NM, CHNO) is a widely studied energetic material, and its decomposition mechanism attracts great interest. In this work, bimolecular reactions between NO and nine intermediates generated during the decomposition of NM were investigated by computational chemistry methods. The mechanisms of the reactions were analyzed.

Theoretical study of the reaction mechanism of CH₃NO₂ with NO₂, NO and CO: the bimolecular reactions that cannot be ignored.

The intriguing decompositions of nitro-containing explosives have been attracting interest. While theoretical investigations have long been concentrated mainly on unimolecular decompositions, bimolecular reactions have received little theoretical attention. In this paper, we investigate theoretically the bimolecular reactions between nitromethane (CH3NO2)-the simplest nitro-containing explosive-and its decomposition products, such as NO2, NO and CO, that are abundant during the decomposition process of CH3NO2.

Theoretical prediction of the reaction of s-triazine with nitrate radical: a new possible route to generate oxy-s-triazine.

Oxy-s-triazine (OST) is one of the important Hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) decomposition products, while it is yet not fully clear how it is formed up to now. The study systematically investigates the reaction of s-triazine (TAZ) with nitrate radical (NO(3)) using computational chemistry methods, for which three entrance channels are devised, resulting in the formation of four isomers of OST. Based on the analysis of the barrier heights and the reaction exothermicities, the pathway to form OST3 through hydrogen atom abstraction and rebound mechanism is likely to be the main channel in the reactions of TAZ with NO(3) radical.

Phase transition and chemical decomposition of shocked CO-N2 mixture.

Using quantum molecular dynamics simulations based on density functional theory including dispersion corrections (DFT-D), we have studied the thermophysical properties of liquid carbon monoxide and nitrogen (CO-N(2)) mixture under extreme conditions. Density functional theory (DFT) method significantly overestimates the pressure as compared to DFT-D. It is demonstrated that the van der Waals (vdW) interaction has a negative contribution to the pressure and tends to reduce the overestimation of the equilibrium volume.

Reactive molecular dynamics simulation of solid nitromethane impact on (010) surfaces induced and nonimpact thermal decomposition.

Which is the first step in the decomposition process of nitromethane is a controversial issue, proton dissociation or C-N bond scission. We applied reactive force field (ReaxFF) molecular dynamics to probe the initial decomposition mechanisms of nitromethane. By comparing the impact on (010) surfaces and without impact (only heating) for nitromethane simulations, we found that proton dissociation is the first step of the pyrolysis of nitromethane, and the C-N bond decomposes in the same time scale as in impact simulations, but in the nonimpact simulation, C-N bond dissociation takes place at a later time.

GCMC investigation into adamantane-based aromatic frameworks with diamond-like structure as high-capacity hydrogen storage materials.

A new class of 3D adamantane-based aromatic framework (AAF) with diamond-like structure was computationally designed with the aid of density functional theory (DFT) calculation and molecular mechanics (MM) methods. The hydrogen storage capacities of these AAFs were studied by the method of grand canonical Monte Carlo (GCMC) simulations. The calculated pore sizes of three AAFs reveal that AAF-1 and AAF-2 belong to microporous materials, while AAF-3 is a member of mesoporous materials.

[Line intensities of upsilon2 perpendicular band and the change of intensities with temperature for H12C14N].

The total internal partition sums (TIPS) were calculated for H12C14N with the product approximation. For rotational partition sums Q(rot), the centrifugal distortion corrections were taken into account. The calculation method for the vibrational partition sums Q(vib) is the harmonic oscillator approximation.

Calculations of bond dissociation energies and dipole moments in energetic materials using density-functional methods.

We compare the effectiveness of six exchange/correlation functional combinations (Becke/Lee, Yang and Parr; Becke-3/Lee, Yang and Parr; Becke/Perdew-Wang 91; Becke-3/Perdew-Wang 91; Becke/Perdew 86; Becke-3/Perdew 86) for computing C-N, O-O and N-NO2 dissociation energies and dipole moments of five compounds. The studied compounds are hexabydro-1,3,5-trinitro-1,3,5-triazine (RDX), dimethylnitramine, cyanogen, nitromethane and ozone. The Becke-3/Perdew 86 in conjunction with 6-31G** is found to give the best results, although for the dipole moments of RDX, there is a slightly difference that B3P86/6-31G** is less reliable than B3P86/6-31+G**.