Vibrational Energy Distribution Research Articles

Theoretical Investigation of N (p-n alkyloxy benzylidene) p-n alkyl aniline Schiff-Based Liquid Crystal Molecule

The primary objective of this article is to investigate the different physical properties of N (p-n alkyloxy benzylidene) p-n alkyl aniline liquid crystalline compound using a quantum mechanical computational method. The identified compound is used to determine the calamitic liquid crystal behavior and is classified within the nO.m family. The optimized structure of the molecule has been obtained using the DFT technique and the functional B3LYP/6-311G++(d,p) and 6-31G++(d,p) basis sets. Using this optimized structure, different reactivity, NLO, vibrational and thermodynamic parameters were calculated and analyzed. It was observed that the compound is showing a lower HOMO-LUMO energy gap value of 4.14 eV (for B3LYP/6-311G++(d,p)) and 4.11 eV (for B3LYP/6-311G++(d,p)), as a result it is easily polarizable. TD- DFT technique has been used to obtain and analyze the UV–Vis spectra. Vibrational Energy Distribution Analysis (VEDA) software was used to perform the Potential Energy Distribution (PED) function of FT-IR and Raman spectra.

A facile synthesis, characterization, DFT, ADMET and in-silico molecular docking analysis of novel 4-ethyl acridine-1,3,9 (2,4,10H)-trione

A novel synthetic reaction was employed to produce an acridine derivative of 4-ethyl acridine-1,3,9 (2,4,10H)-trione. The structural characterizations of the synthesized compound were confirmed through FT-IR, NMR 1H,13C, and GC-Mass spectral data. Furthermore, the DFT approaches were performed to the vibrational wavenumbers obtained through simulation with experimental wave numbers. The Vibrational Energy Distribution Analysis (VEDA) software is employed in FT-IR wave number for conducting potential energy decomposition (PED) analysis. DFT calculations were also applied to optimize the structural parameters and investigate Frontier molecular orbitals (FMOs), molecular electrostatic potentials, RDG studies, and global chemical reactivity descriptors, Natural bond orbital analysis and Non-linear optical properties were obtained for the title compound using the DFT method. Molecular docking studies were conducted to explore the binding mode mechanism of title compound and were evaluated for cancer-related proteins, specifically 4y72. Also, the synthesised compound was evaluated for Drug-likeness, and ADMET (Absorption, Distribution, Metabolism, Excretion, and Toxicity) properties indicating favourable pharmacokinetic profiles with no observed signs of toxicity.

Investigation on the vibration localization of mistuned bladed disk with frictional contact

The mistuning phenomenon is commonly seen in the bladed assemblies of turbomachinery, leading to an unreasonably localized energy distribution that may increase the risk of high cycle fatigue and potentially cause blade failure. The friction coupling interaction is often introduced to attenuate the effect of excessive amplification on the structural vibration. To investigate the vibration localization of damped and mistuned bladed-disk system, a typical mistuning characterization is applied to an improved four-degree-of-freedom lumped parameter model to explicit the vibratory properties with coupled frictional contact. The statistical findings of natural frequency and modal localization factor are obtained by employing the Monte Carlo simulation to explore the influence of mistuned variance and coupled stiffness on the modal localization of free and damped bladed-disk system, respectively. The forced response sensitivity featured in the mistuned variance is quantitatively analyzed from the perspective of vibration localization and energy distribution by the nonlinear solution method. The influence of excitation order and normal load are further, respectively, discussed on the response localization level of the mistuned system. The results can provide fundamental knowledge of the impact of the mistuning pattern on vibration localization for the early design of the aeroengine.

Detailed quasiclassical dynamics of the F- + SiH3Cl multi-channel reaction.

We report a detailed quasiclassical trajectory study on the F- + SiH3Cl multi-channel reaction using a full-dimensional ab initio analytical potential energy surface. Reaction probabilities, cross sections, initial attack and scattering angle distributions as well as product relative translational, internal, vibrational, and rotational energy distributions are obtained in the collision energy range of 1-40 kcal mol-1 for the following channels: SiH3F + Cl-, SiH2Cl- + HF, SiH2F- + HCl, SiH2FCl + H-, SiH2 + FHCl-, and SiHFCl- + H2. All the channels are translationally cold indicating indirect mechanisms, except proton transfer (SiH2Cl- + HF), which shows mixed direct-indirect character. The angular distributions vary depending on collision energy and inversion/retention for SiH3F + Cl-. In the case of SiH2Cl- + HF front-side/back-side attack backward-forward/forward scattering preference is found at low/high collision energy. SiH2F- + HCl is formed with isotropic scattering and the preferred angle of attack is similar to the SiH3F + Cl- channel. SiH2FCl + H-/SiH2 + FHCl- favors back-side attack and isotropic/backward scattering, whereas SiHFCl- + H2 does not show significant angular preference.

Solvent effects on spectroscopic, electronic, and topological analyses, Hirshfeld surface, ADME, and molecular docking studies on antiviral pyridine carboxamide derivatives

A theoretical study of three pyridine carboxamide derivatives in conjunction with the Density Functional Theory (DFT) approach at the 6-311+G(d,p) basis set is presented along with X-ray results. The pyridine carboxamide derivatives were analyzed with the help of FT-IR, UV–Vis, 1H and 13C NMR investigation. The spectral characterizations were made by vibrational energy distribution analysis (VEDA4), which helps to assign vibrational frequencies to specific molecular vibrations. A comparative analysis of computed 1H and 13C NMR chemical shift values with experimental chemical shifts for the pyridine carboxamide compounds by applying the gauge-including atomic orbitals method in chloroform and acetone solvents was carried out. UV–Vis spectroscopy and electronic transitions were conducted on both chloroform and acetone solvents through the assistance of the TD-DFT methodology. Hirshfeld Surface analysis was employed to analyze the intermolecular hydrogen bonds of the type N-H⋯N to the crystal packing. The chemical properties of frontier molecular orbital and global reactivity descriptors were analyzed for the different solvents such as chloroform and acetone. The Fukui functions were used to identify reactive sites in a molecule, including those susceptible to nucleophilic and electrophilic outbreaks. The weak interactions were analyzed using reduced density gradient (RDG) analysis, a computational method used to study noncovalent interactions, including hydrogen bonding. The Absorption, Distribution, Metabolism, and Excretion (ADME) attributes of the studied compounds have been evaluated for drug discovery initiatives. Molecular docking studies with antiviral SARS-CoV-2 Mpro and Omicron variant containing the Q493R mutation proteins of three pyridine carboxamide derivatives (L3–L5) have been performed, and L5 has maximum binding energy values of −7.13 kcal/mol for 6LU7.

Influence of Fastener Stiffness and Damping on Vibration Transfer Characteristics of Urban Railway Bridge Lines Using Vibration Power Flow Method

The problem of vibration in urban rail transportation has become a current research hotspot. When a train passes through a bridge line at high speed, it interacts with the rail, leading to vibration energy transfer and causing issues such as vibration and noise in the line infrastructure. To propose a more targeted vibration-damping track structure, it is necessary to explore the vibration characteristics of urban rail transit bridge lines and understand the regulations governing the distribution of vibration energy. This paper employs the theory of vehicle–rail–bridge interaction to establish a coupled dynamics model for a subway A-type vehicle–integral ballast bed–box girder bridge. Based on the proposed model, the transmission characteristics and distribution of vibration energy in the rail–bridge system are systematically analyzed and the influence of the parameters of the track structural components on the power flow of the system are investigated. The results of this study indicate that low-frequency vibration energy in the track system of urban rail transit bridges is primarily concentrated within the track structure, whereas high-frequency vibration energy is mainly focused on the rail. The fastener, as a component connecting the rail and the overall roadbed, has different effects on the peak value of the power flow and the accumulation of vibration energy in various components such as the rail, the overall roadbed, the top plate of the box girder bridge, and the bottom plate in different frequency bands due to its own stiffness and damping. An appropriate increase in fastener damping is beneficial for reducing the accumulation of low-frequency vibration energy in the track structure.

Methyl 4-pyridyl ketone thiosemicarbazone (4-PT) as an effective and safe inhibitor of mushroom tyrosinase and antibrowning agent

Enzymatic browning is of concern as it can affect food safety and quality. In this study, an effective and safe tyrosinase inhibitor and anti-browning agent, methyl 4-pyridyl ketone thiosemicarbazone (4-PT), was synthesised and characterised using Fourier-transform infrared (FTIR) spectroscopy, CHNS elemental analysis, and proton (1H) and carbon-13 (13C) nuclear magnetic resonance (NMR) spectroscopy. The vibrational frequencies of 4-PT were studied theoretically using vibrational energy distribution analysis (VEDA). Density functional theory (DFT) was applied to elucidate its chemical properties, including the Mulliken atomic charges, molecular electrostatic potential (MEP), quantum theory of atoms in molecules (QTAIM) and reduced density gradient non-covalent interactions (RDG-NCIs). Moreover, 4-PT was compared with kojic acid in terms of its effectiveness as a tyrosinase inhibitor and anti-browning agent. The toxicity and physicochemical properties of 4-PT were predicted via ADME evaluation, which proved that 4-PT is safer than kojic acid. Experimentally, 4-PT (IC50 = 5.82 μM, browning index (10 days) = 0.292 ± 0.002) was proven to be an effective tyrosinase inhibitor and anti-browning agent compared to kojic acid (IC50 = 128.17 μM, browning index (10 days) = 0.332 ± 0.002). Furthermore, kinetic analyses indicated that the type of tyrosinase inhibition is a mixed inhibition, with Km and Vmax values of 0.85 mM and 2.78 E-09 μM/s, respectively. Finally, the mechanism of 4-PT for tyrosinase inhibition was proven by 1D, second derivative and 2D IR spectroscopy, molecular docking and molecular dynamic simulation approaches.

Defect detection and imaging in elastic materials with complex geometries

Additive manufacturing has made it possible to easily create parts with complex shapes, even out of metal materials. However, in order to guarantee the quality of such parts, there is a need to establish a nondestructive inspection technique that is feasible for such complex structures. In this presentation, I will introduce a technology that can visualize internal damage even in complex objects by utilizing the ultrasonic field generated and diffused inside the object with non-contact manner. Ultrasonic waves generated by laser irradiation resonate with the natural frequency of defects such as delamination near the surface of an object. By scanning the laser beam for generating ultrasonic waves and detecting vibrations at a fixed position on the surface of the object, an image of defects in the vicinity of the surface can be obtained as a distribution of vibration energy. The distribution of vibration energy does not depend on reflected or scattered waves from the object's wall, but only on information from the point where the laser is irradiated. This technique is expected to be especially useful for in-situ inspections of the additive manufacturing objects.

Experimental and theoretical investigation of structure activity relationship on L-Lysine Monohydrate for antioxidant efficacy

Comprehensive spectroscopic research has been undertaken to investigate the structural behaviour of the l-lysine monohydrate molecule. The spectral properties of the l-lysine monohydrate molecule in solid phase were examined using Fourier Transform Infrared (FTIR) and Fourier Transform Raman methods. The B3LYP/6–311++G (d, p) computations were used to optimize the structure of the molecule. To provide complete vibrational spectral assignments, vibration energy distribution analysis (VEDA) was used. The Natural bond orbital (NBO) analysis explains the stability and distinct forms of hydrogen bonds with in the molecule. The chemical stability of the molecule is predicted by Highest Occupied Molecular Orbital (HOMO) and Lowest Unoccupied Molecular Orbital (LUMO) analysis. Non-Covalent Interaction (NCI) analysis was done to identify weak interactions according to density of electron of the title compound. The fukui function identified the chemical reactivity sites. To predict its antioxidant efficacy, docking studies were done.

Computational Study on Piperazine‐1,4‐Diium Acetate Using Dft Investigations: Structural Aspects, Topological and Nonlinear Optical Properties

AbstractThe work aims to investigate the nonlinear optical (NLO) activity of piperazine‐1,4‐diium acetate (PAA) molecule utilizing computational techniques. The computational calculations are performed using density functional theory (DFT) to explore the vibrational modes, electronic and NLO properties of PAA by comparing them with piperazine and acetic acid molecules. The natural bond orbital analysis is performed to identify hydrogen bonding and charge transfer interaction. A vibrational analysis is carried out and the assignment of fundamental modes is done using the vibrational energy distribution analysis (VEDA) program. Molecular electrostatic potential, frontier molecular orbital, electron localization function, localized orbital locator and Fukui analysis are carried out to identify chemical reactivity and charge transfer interaction. The UV–visible analysis is performed to obtain the electronic absorption spectrum. The hole–electron analysis is performed for the first five excitations to identify the type of excitation. The atoms in molecules, reduced density gradient and independent gradient model are performed to identify the hydrogen bonding, steric and van der Waals interactions. Hirshfeld analysis is performed to explore the intermolecular interactions within the PAA molecule. The NLO calculation is performed to evaluate the NLO parameters. The obtained results show that the PAA molecule is suitable for NLO applications.

First principles simulation of reacting hypersonic flow over a blunt wedge

This article presents molecular-level analysis of a reactive, near-continuum, Mach 21 nitrogen flow over a blunt wedge using the direct molecular simulation (DMS) method. The flow conditions lead to internal energy excitation and dissociation in the flow field, resulting in thermal and chemical nonequilibrium in the flow. Thermal nonequilibrium in the vibrational mode is observed to extend to the molecular level, where the vibrational energy distributions at various points in the flow field are observed to be non-Boltzmann. Furthermore, this is the first reactive DMS calculation where the wall is assumed to be isothermal and full momentum accommodation of the particles is enforced, hence incorporating viscous wall effects. Since the DMS method uses a quantum mechanically generated interaction potential as its only modeling input, all thermochemical and transport properties of the flow field can directly be attributed to the ab initio potential energy surface. Using the DMS solution as a benchmark, this article assesses the performance of Navier–Stokes computational fluid dynamics solutions using lower fidelity two-temperature models. Two models are chosen as points of comparison: the well-known Park two-temperature model and the recently developed modified Marrone and Treanor model.

Assessing Mixed Quantum-Classical Molecular Dynamics Methods for Nonadiabatic Dynamics of Molecules on Metal Surfaces.

Mixed quantum-classical (MQC) methods for simulating the dynamics of molecules at metal surfaces have the potential to accurately and efficiently provide mechanistic insight into reactive processes. Here, we introduce simple two-dimensional models for the scattering of diatomic molecules at metal surfaces based on recently published electronic structure data. We apply several MQC methods to investigate their ability to capture how nonadiabatic effects influence molecule-metal energy transfer during the scattering process. Specifically, we compare molecular dynamics with electronic friction, Ehrenfest dynamics, independent electron surface hopping, and the broadened classical master equation approach. In the case of independent electron surface hopping, we implement a simple decoherence correction approach and assess its impact on vibrationally inelastic scattering. Our results show that simple, low-dimensional models can be used to qualitatively capture experimentally observed vibrational energy transfer and provide insight into the relative performance of different MQC schemes. We observe that all approaches predict similar kinetic energy dependence but return different vibrational energy distributions. Finally, by varying the molecule-metal coupling, we can assess the coupling regime in which some MQC methods become unsuitable.

(1E)-1-(2-pyrazinyl)ethanone thiosemicarbazone (PT) as a tyrosinase inhibitor with anti-browning activity: Spectroscopy, DFT and molecular docking studies

In this study, (1E)-1-(2-Pyrazinyl)ethanone thiosemicarbazone (PT) was synthesized and characterized using Fourier-transform infrared (FTIR), ultraviolet-visible (UV–Vis), proton nuclear magnetic resonance (1HNMR ) and carbon-13 nuclear magnetic resonance (13CNMR ) spectroscopy. The vibrational frequencies were analysed using the Vibrational Energy Distribution Analysis (VEDA) program. The chemical properties of PT, including electron density distribution and intramolecular interactions, were characterized using in-silico methods based on Mulliken atomic charges, molecular electrostatic potential (MEP), quantum theory of atoms in molecules and reduced density gradient noncovalent interaction approaches. PT exhibits a significant inhibitory effect on enzymatic browning (6 and 24 h) and tyrosinase enzymes (IC50 = 7.75 μM). Kinetic analysis shows that PT is a mixed-type inhibitor, with respective Km and Vmax values of 0.632 mM and 0.0044 μM/s, and that it forms a reversible enzyme-inhibitor interaction. The PT-tyrosinase interaction was experimentally evaluated based on 1D, second derivatives of 1D, 2D and 3D IR spectroscopy. Furthermore, analysis of absorption, distribution, metabolism, excretions and toxicity properties revealed good physicochemical properties of PT according to the drug scores and Lipinski's Rule of Five. Lastly, the mechanisms of PT against tyrosinase were visualized and supported by means of a molecular docking approach.

Experimental and computational studies of organic 4-[[(4-chlorophenyl)imino]methyl]phenol single crystals for optic and biological applications

The organic 4-[[(4-chlorophenyl)imino]methyl]phenol single crystals were grown by slow evaporation growth technique. Single crystal X-ray diffraction (XRD) studies reveal that the grown crystal belongs to an orthorhombic crystal system with centrosymmetric space group Pbcn. The molecular geometric parameters and the vibrational frequencies of the grown crystal were calculated with the aid of density functional theory (DFT). The detailed interpretation of FTIR and FT-Raman spectra was carried out with the help of vibrational energy distribution analysis (VEDA 4.0) and the wavenumbers were scaled by the wavenumber linear scaling (WLS) method. The UV–Vis spectrum was recorded in the range of 200–800 nm. The intramolecular electronic transitions and their stabilization energy were carried out using NBO analysis. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) and their energy gap values were calculated by the computational analysis of the molecule using the DFT approach. Hirshfeld surface analysis was carried out to identify the intermolecular interactions visibly. The thermogravimetric (TG) and differential thermal analyses (DTA) techniques were used to determine the thermal properties of the grown crystal. The kinetic and thermodynamic parameters were calculated using the Coats-Redfern and Broido methods. The electron localization descriptors, such as the Electron Localization Function (ELF) and the Localized Orbital Locator (LOL), are calculated. Reduced Density Gradient (RDG) analysis was used to identify the non-covalent interactions. A molecular docking study was performed using six protein receptors. The antidiabetic activities were analyzed.

Phase-based vibration imaging for structural dynamics applications: Marker-free full-field displacement measurements with confidence measures

Inspired by the concept of thermal imaging, we develop a phase-based vibration imaging technique using marker-free full-field displacement measurements, which aims to determine vibrational energy distribution and possibly vibration parameters as the thermal imaging determining thermal energy distribution using colormap. In this study, accurate full-field measurements are conducted at the sub-pixel level by performing a full-field phase-based optical flow with three novel progresses. First, an image-preprocessing Gaussian smoothing gradient is applied to reduce the nonlinear phase caused by homogenous patterns and image noise. Second, two confidence measures (phase nonlinearity and filter response) are adopted to obtain reliable displacement measurements estimated from the multi-scale and multi-direction phases. Third, the combination of vector average and the intersection of constraints ensure the accuracy of integrating every pixel’s displacement components. The vibrations can then be imaged by analyzing the acquired full-field displacements using techniques such as mean absolute deviation and frequency analyses. The capability of the proposed technique is demonstrated through numerical experiments using artificial patterns. After then, experimental validation is performed, which includes full-field operational deflection shape extraction on a 5-story structure and vibration imaging of an in-service hydrogen charging station, further proving the effectiveness of the proposed vibration imaging technique.

Nascent Vibrational Energy Distribution of CS(X1Σ+) Generated in the S(1D) + CS2 Reaction.

The internal energy distributions of reaction products are important information in clarifying the mechanism of chemical reactions. There are few reports of the nascent vibrational energy distribution of CS(X1Σ+) generated in the S(1D) + CS2 reaction. As long as S(1D) is produced by photodissociation of CS2, CS(X1Σ+), as a product of the chemical reaction and as a photoproduct of CS2 is indistinguishable. In this study, S(1D) was generated by the photolysis of OCS at 248 nm, where CS2 hardly dissociates, and CS(X1Σ+) was generated only by the S(1D) + CS2 reaction. The vibrational levels v″ = 0-6 of CS(X1Σ+) were detected with laser-induced fluorescence (LIF) via the A1Π-X1Σ+ transition. The identical time profiles of the LIF intensities showed that all the vibrational levels were produced by the S(1D) + CS2 reaction. The relative nascent vibrational populations of CS(X1Σ+) determined from the area intensities of the excitation spectra are 1.00 ± 0.11/0.58 ± 0.06/0.31 ± 0.03/0.078 ± 0.009/0.013 ± 0.001/<0.002/<0.002 (the values for v″ = 5 and 6 are the upper limits) for v″ = 0/1/2/3/4/5/6. The distribution agrees well with the statistical (prior) distribution.

DFT study of molecular interaction between Menthol and Myristic Acid

Menthol is used to treat minor aches and pains of the joints and muscles, whereas Myristic Acid is a surfactant, emulsifier and cleansing agent and plays various roles in the cosmetic industry, even as a lubricant. Considering their extensive pharmaceutical usage and cosmetic value, the molecular interaction between Menthol and Myristic Acid is investigated in our current work. Density Functional Theory at B3LYP/6–311 + G (d, p) basis state is employed to study the interacting mechanisms of the two compounds. The occurrence of a charge transfer path between Menthol and Myristic Acid is confirmed by second-order delocalization energies E(2) using the natural bond orbital (NBO) study. The atom in molecule (AIM) study is performed using Multiwfn Software. Thefrontier molecular orbitals(FMOs) and molecularelectrostatic potential(MEP) of the complex were analyzed by theoretical calculations. The detailed analysis of the vibrational spectra has been carried out using the Vibrational Energy Distribution Analysis (VEDA) program. The theoretical and experimental FTIR vibrational spectra are compared and found in good correlation. Molecular docking analysis of the complex with the protein receptor 5KF4 PDB ID has been performed using Autodock tool and binding energy is −4.07 kcal/mol.

Studies on crystal growth, experimental, structural, DFT, optical, thermal and biological studies of 3-hydroxy-4-methoxybenzaldehyde single crystals

The organic 3-hydroxy-4-methoxybenzaldehyde single crystal has been grown by the slow evaporation technique. Single crystal X-ray diffraction (XRD) study shows that the grown crystal belongs to a monoclinic crystal system with centrosymmetric space group P21/c. The spectral analysis of 3-hydroxy-4-methoxybenzaldehyde calculations was performed with the help of DFT at the B3LYP/6-311 + G(d,p) level of theory. The experimental results of FTIR and FT-Raman were compared with the computational results. Detailed interpretations of the vibrational spectra were carried out with the aid of vibrational energy distribution analysis using potential energy distribution (PED) analysis and vibrational wavenumber scaled by the WLS (Wavenumber Linear Scaling) method. The natural bond orbital (NBO) analysis was carried out to identify intramolecular hydrogen bonding. The optical properties of the grown crystal were analyzed by UV–Visible studies. Photoluminescence studies show that the high-intensity peak observed around 410 nm. The laser damage threshold value of the grown crystal has been determined using an Nd:YAG laser operating at 1064 nm. The HOMO (Highest Occupied Molecular Orbital) – LUMO (Lowest Unoccupied Molecular Orbital) was used to identify the energy gap. Hirshfeld Surface (HS) analysis was used to determine the intermolecular interactions. The thermal properties of the grown crystal were performed by Thermogravimetric (TG) and Differential thermal analyses (DTA). The kinetic and thermodynamic parameters were calculated. The surface morphology of the grown crystal was studied by using Scanning Electron Microscopy (SEM) analysis. The antibacterial and antifungal studies were analyzed.

Theoretically Revealing the Response of Intermolecular Vibration Energy Transfer and Decomposition Process of the DNTF System to Electric Fields Using Two-Dimensional Infrared Spectra.

The external electric field (E-field), which is an important stimulus, can change the decomposition mechanism and sensitivity of energetic materials. As a result, understanding the response of energetic materials to external E-fields is critical for their safe use. Motivated by recent experiments and theories, the two-dimensional infrared (2D IR) spectra of 3,4-bis (3-nitrofurazan-4-yl) furoxan (DNTF), which has a high energy, a low melting point, and comprehensive properties, were theoretically investigated. Cross-peaks were observed in 2D IR spectra under different E-fields, which demonstrated an intermolecular vibration energy transfer; the furazan ring vibration was found to play an important role in the analysis of vibration energy distribution and was extended over several DNTF molecules. Measurements of the non-covalent interactions, with the support of the 2D IR spectra, indicated that there were obvious non-covalent interactions among different DNTF molecules, which resulted from the conjugation of the furoxan ring and the furazan ring; the direction of the E-field also had a significant influence on the strength of the weak interactions. Furthermore, the calculation of the Laplacian bond order, which characterized the C-NO2 bonds as trigger bonds, predicted that the E-fields could change the thermal decomposition process of DNTF while the positive E-field facilitates the breakdown of the C-NO2 in DNTFⅣ molecules. Our work provides new insights into the relationship between the E-field and the intermolecular vibration energy transfer and decomposition mechanism of the DNTF system.

Post-reaction internal energy distributions of quantum-kinetics model for simulating chemical reactions of polyatomic molecules

Chemical reactions significantly influence aerodynamic performance during spacecraft entry into the Martian atmosphere. Several chemical reaction models have been proposed in the direct simulation Monte Carlo simulation. The quantum-kinetics (Q-K) model has been applied in the case of diatomic molecules. Given that the Martian atmosphere consists primarily of CO2, it is crucial to find ways of implementing the Q-K model for polyatomic molecules. Although the chemical reaction rates involving CO2 have been investigated using the Q-K model, the problem of achieving detailed balance remains. Multiple vibrational modes exist for polyatomic molecules. Under the Q-K distribution, the average vibrational level of each mode is higher than that under the equilibrium distribution, and the total energy may be insufficient. Hence, its applicability to polyatomic molecules needs to be revealed. In this study, a comparison is made of the respective results obtained using the Larsen–Borgnakke (L–B) and Q-K distribution methods for the energy distribution of the reaction CO2+O⇋CO+O2, and the detailed balance is achieved with the Q-K method but not the L–B method. Under the conditions assumed in this study, the vibrational energy distribution of CO consumed by the reverse reaction is not in good agreement with that generated by the forward reaction, leading to the failure of the L–B method. Finally, the results indicate that the detailed balance is reached only when the collision temperature, based on the translational and vibrational energy, is employed to adjust the activation energy rather than the translational temperature generally adopted in the literature.