Lennard-Jones Potential Energy Research Articles

Elastic Wave Propagation in 2D Carbon Nano‐Onion Lattices

AbstractThis study presents a simple analytical model to investigate wave propagation in 2D carbon nano‐onions (CNOs) and nitrogen‐doped carbon nano‐onions (N‐CNOs) lattices. Furthermore, the dispersion relationships of the waves and bandgaps in these lattices are derived based on Bloch's theorem. The CNOs and N‐CNOs lattices are modeled as infinite 2D mass‐in‐mass structures accurately assembled using linear springs. The Lennard–Jones potential energy is employed to obtain equivalent spring constants. A key finding of this research is the identification of bandgaps within all lattice structures, signifying regions where wave propagation is prohibited. The existence of these bandgaps offers potential for the advancement of adjustable nano‐scale metamaterials.

An equivalent surface model bridging intermolecular interactions and the normalization of substrate wettability

A liquid deposited on a solid surface exhibits various wetting properties, primarily influenced by solid–liquid intermolecular interactions. Achieving a well-estimation of wetting behaviors on textured surfaces remains challenging because the influence of surface textures on intermolecular interactions is unclear. Here, an equivalent surface model is proposed to unify the wettability of both plane and textured substrates through intermolecular interactions. We show that by incorporating intermolecular interactions, lattice structures, and surface topographies, the substrate wettability can be tailored in an equivalent plane with the same average Lennard–Jones potential energy field E. The wettability of one substrate (plane or patterned) is transferred from non-wetting, partial wetting to complete wetting by adjusting the potential well depth of E, εa. With enhancing εa, complete wetting is achieved under the critical potential well depth of E, εac. Before εac, the spreading radius grows as R ∼ t1/1.47 until reaches equilibrium. In this scenario, the equilibrium contact angle θ and spreading factor β are strongly dependent on εa, and cos θ is linear to εa. When exceeding εac, complete wetting is achieved, and droplets spread with a precursor film as R ∼ t1/2.3 latterly. This model builds a bridge to link intermolecular interactions and substrate wettability normalization. This strategy offers a framework for substrate surface design and wettability manipulation, catering to applications such as photoresist-drop dispensing in nanoimprint lithography, surface design for grating antifouling, and anti-icing on aircraft surfaces.

Exploring HCl-HCl interactions: QZVPP calculations, improved Lennard-Jones potential, and second virial coefficient analysis for thermodynamics and industrial applications.

In this paper, we present a comprehensive analysis of HCl-HCl interactions, including QZVPP calculations, energy fitting, conformation validation, and the determination of the second virial coefficient B using improved Lennard-Jones (ILJ) potential parameters. To acquire accurate interaction energies, initial QZVPP calculations are performed on approximately 1851 randomly generated HCl-HCl conformations. Then, these energies are used to fit an improved Lennard-Jones potential energy surface, allowing for a robust description of HCl-HCl interactions. The ILJ potential parameters are then used to validate particular HCl dimer conformations, ensuring their stability and consistency with experimental observations. The correlation between calculated and experimental conformations strengthens the validity of the ILJ potential parameters. In addition, the second viral coefficient B is calculated at various temperatures using the ILJ potential. The obtained B values are compared to experimental data, demonstrating close agreement, and validating the ILJ potential's ability to accurately capture the intermolecular interactions and gas-phase behavior of the HCl-HCl system. The results of this study demonstrate the effective implementation of QZVPP calculations, energy fitting, and ILJ potential parameters in validating HCl-HCl conformations and accurately determining the second virial coefficient B. The high degree of concordance between calculated B values and experimental data demonstrates the validity of the ILJ potential and its suitability for modeling HCl-HCl interactions. This research contributes to a greater comprehension of HCl-HCl interactions and their implications for numerous chemical and atmospheric processes. The validated conformations, energy fitting method, and calculated second virial coefficients provide valuable instruments for future research and pave the way for more accurate modeling and simulations of HCl-HCl systems.

Research on azeotropic breaking extraction technology for High-Value chemicals from wash oil

In response to the challenge of achieving high-purity separation within a mixture containing acenaphthene, dibenzofuran, fluorene, and biphenyl in coal tar wash oil fractions, the azeotropic behavior of this mixture was investigated through phase equilibrium experiments to elucidate the azeotropic system. Once the azeotropic system was identified, attention shifted to intermolecular forces, and simulation calculations utilizing the Lennard-Jones potential energy function were employed to reveal the mechanism underlying high-purity separation in the azeotropic system. Building upon this foundation, the feasibility of solvent crystallization was explored as a means to break the azeotrope and achieve high-purity separation. This involved a thorough analysis of the intermolecular interactions between the crystallization solvent and the mixture system. Ethanol, methanol, and pentanol were chosen as potential solvents for conducting solvent crystallization experiments.Results demonstrate that ethanol performs admirably within the solvent crystallization method, exhibiting a high degree of crystallization selectivity for acenaphthene. On the other hand, pentanol demonstrates advantages in the separation and crystallization for removing biphenyl. Using ethanol as the solvent for crystallization, the acenaphthene content can be refined to 99.17%, while the biphenyl content can be reduced to a mere 0.002%. These findings underscore the effectiveness of ethanol as a solvent in effectively addressing the azeotropic challenge arising from the coexistence of biphenyl and acenaphthene, ultimately achieving an efficient separation of the targeted substances. Considering both crystallization selectivity and yield, ethanol emerges as the most suitable crystallization solvent for this intricate multi-component system. This study presents a practical solution for the efficient separation of acenaphthene, dibenzofuran, fluorene, and biphenyl—all of which constitute azeotropic systems within the heavy distillate fraction of wash oil.

RETRACTED:Exploring the intermolecular interactions in carbon disulfide dimer: An ab initio study using an improved Lennard–Jones potential energy surface for physical insights

AbstractCarbon disulfide dimer (CS2)2 is a model system that has been widely studied in the field of computational chemistry because of its relevance to a variety of chemical and biological processes. The (CS2)2 dimer is a relatively simple molecular system composed of two carbon disulfide (CS2) molecules interacting with each other through intermolecular forces. Despite its apparent simplicity, the (CS2)2 dimer exhibits a rich array of structural and dynamical properties that are of great interest to researchers. In this research, we present an ab initio study of the intermolecular interactions in the carbon disulfide dimer (CS2)2 using an improved Lennard–Jones (ILJ) potential with CCSD(T)/QZVPP calculations. The potential energy surface of (CS2)2 is calculated using high‐level quantum mechanical calculations based on the CCSD(T)/def2‐qzvpp method, which accurately accounts for electron correlation effects. The resulting potential energy surface is then fitted to an ILJ potential energy function, which includes both long‐range dipole–dipole interactions and short‐range repulsive interactions. The calculated potential energy surface reveals a rich variety of structural and dynamical properties of (CS2)2, including multiple minima and saddle points, which are sensitive to the relative orientation of the two CS2 molecules. It is essential to use extended basis sets to accurately incorporate the significant quadrupole moment of CS2, which we have calculated to be 2.44 a.u. The results of this study demonstrate the importance of using high‐level ab initio methods for the accurate calculation of potential energy surfaces in complex molecular systems such as (CS2)2. The use of an ILJ potential, which takes into account both dipole–dipole interactions and short‐range repulsive interactions, provides a more accurate and efficient approach for modeling intermolecular interactions in (CS2)2 and other similar systems. The results of this study will be useful for understanding the behavior of carbon disulfide dimers in different environments and for the development of new materials and chemical processes.

Investigation of fullerene motion on thermally activated gold substrates with different shapes

In the current study, the regime of motion of fullerene molecules on substrates with different shapes at a range of specific temperatures has been investigated. To do so, the potential energy of fullerene molecules was analyzed using the classical molecular dynamics method. C20, C36, C50, C60, C72, C76, C80, and C90 fullerene molecules were selected due to their spherical shapes with different sizes. In addition, to completely analyze the behavior of these molecules, different gold substrates, including flat, concave, the top side of the step (upward step), and the downside of the step (downward step) substrates, were considered. Specifying the regime of the motion at different temperatures is one of the main goals of this study. For this purpose, we have studied the translational and rotational motions of fullerene molecules independently. In the first step of the investigation, Lennard-Jones potential energy of fullerene molecules was calculated. Subsequently, the regime of motion of different fullerenes has been classified, based on their displacement and sliding velocity. Our findings indicated that C60 is appropriate in less than 5% of the conditions. However, C20, C76 and C80 molecules were found to be appropriate candidates in most cases in different conditions while they were incompetent only in seven situations. As far as a straight-line movement is considered, the concave geometry demonstrated a better performance compared to the other substrates. In addition, C72 indicated less favorable performance concerning the range of movement and diffusion coefficients. All in all, our investigation helps to understand the performance of different fullerene molecules on gold substrates and find their probable application, especially as a wheel in nano-machine structures.

Water molecules in CNT-Si3N4 membrane: Properties and the separation effect for water-alcohol solution.

Water confined in carbon nanotubes (CNTs) has been intensively studied because of its unique properties and potential for various applications and is often embedded in silicon nitride (Si3N4) membranes. However, the understanding of the influence of Si3N4 on the properties of water in CNTs lacks clarity. In this study, we performed molecular dynamics simulations to investigate the effect of the Si3N4 membrane on water molecules inside CNTs. The internal electric field generated in the CNTs by the pointcharges of the Si3N4 membrane changes the structure and dynamical properties of water in the nanotubes, causing it to attain a disordered structure. The Si3N4 membrane decreases the diffusivity of water in the CNTs; this is because the Coulomb potential energy (i.e., electrostatic interaction) of water decreases owing to the presence of Si3N4, whereas the Lennard-Jones potential energy (i.e., van der Waals interaction) does not change significantly. Furthermore, electrostatic interactions make the water structure more stable in the CNTs. As a result, the Si3N4 membrane enhances the separation effect of the water-methanol mixture with CNTs in the presence of an external electric field. Furthermore, the threshold of the external electric field strength to induce water-methanol separation with CNTs is reduced owing to the presence of a silicon nitride membrane.

A sectional soot formation kinetics scheme with a new model for coagulation efficiency

A sectional scheme for soot formation is combined with a novel model for coagulation efficiency based on the thermal rebound concept and involves the minimisation of the Lennard-Jones potential energy between two colliding particles. Here, a novel generalisation of the interaction potential well depth is formulated for particles of any size or material composition that contains a free parameter λ which is related to the soot particle void fraction. A simplification that expresses the coagulation rate in an Arrhenius-like form is proposed so that the entire gas-phase and soot kinetics can be easily coupled and integrated using existing chemical kinetics solvers. The model is included in the sectional scheme, which accounts for nucleation, surface growth/oxidation, coagulation and fragmentation, and is validated against experimental data for a series of ethylene burner stabilised stagnation (BSS) premixed flames and a methane laminar coflow diffusion flame. The soot kinetics is discretised into lumped species according to soot particle size (or number of carbon atoms) and the soot evolution follows a 23-step abstract reaction scheme that is a reduced form of an existing multisectional soot kinetics scheme (Sirignano et al., Energy & Fuels 27, 2013). Overall, the model predictions produce a satisfactory agreement with the experimental data but there is considerable sensitivity to λ. In particular, λ has a strong effect on the soot particle size distribution (PSD) in the BSS flames. λ=1 or 1.25 lead to an overprediction of large particle concentrations but result in the correct transition to a bimodal PSD as the stagnation plate separation distance increases, whereas λ=2 is found to produce accurate predictions for nascent soot but suppresses the transition to a bimodal PSD. In the methane coflow diffusion flame increasing λ reduces the soot volume fraction but the predictions are also found to be very sensitive to the chosen numerical threshold for the lower soot size detection limit and results are presented for 2 nm and 7 nm thresholds for comparison against both laser-based and probe-based experimental data.

RLDOCK: A New Method for Predicting RNA-Ligand Interactions.

The ability to accurately predict the binding site, binding pose, and binding affinity for ligand-RNA binding is important for RNA-targeted drug design. Here, we describe a new computational method, RLDOCK, for predicting the binding site and binding pose for ligand-RNA binding. By developing an energy-based scoring function, we sample exhaustively all of the possible binding sites with flexible ligand conformations for a ligand-RNA pair based on the geometric and energetic scores. The model distinguishes from other approaches in three notable features. First, the model enables exhaustive scanning of all of the possible binding sites, including multiple alternative or coexisting binding sites, for a given ligand-RNA pair. Second, the model is based on a new energy-based scoring function developed here. Third, the model employs a novel multistep screening algorithm to improve computational efficiency. Specifically, first, for each binding site, we use a gird-based energy map to rank the binding sites according to the minimum Lennard-Jones potential energy for the different ligand poses. Second, for a given selected binding site, we predict the ligand pose using a two-step algorithm. In the first step, we quickly identify the probable ligand poses using a coarse-grained simplified energy function. In the second step, for each of the probable ligand poses, we predict the ligand poses using a refined energy function. Tests of the RLDOCK for a set of 230 RNA-ligand-bound structures indicate that RLDOCK can successfully predict ligand poses for 27.8, 58.3, and 69.6% of all of the test cases with the root-mean-square deviation within 1.0, 2.0, and 3.0 Å, respectively, for the top three predicted docking poses. The computational method presented here may enable the development of a new, more comprehensive framework for the prediction of ligand-RNA binding with an ensemble of RNA conformations and the metal-ion effects.

Dynamics and spectroscopy of van der Waals complexes composed of ammonia and noble gases.

In this work, we calculate the rovibrational energies and spectroscopic constants for the systems formed by ammonia (NH3) and noble gases (Ng=He, Ne, Ar, Kr and Xe). For the spectroscopic constant calculations, we used two different methods: Dunham and another one that use rovibrational energies (here calculated by discrete variable method). In both cases, we used the improved Lennard-Jones potential energy curves (PECs). These PECs, which describe very well van der Waals systems, were built using the dissociation and equilibrium distance obtained from experiments of crossed molecular beams. The spectroscopic constant results, obtained by both methods were in excellent agreement with each other for all NH3-Ng studied systems. Also in relation to NH3-He system, we realize that although this system has a relatively small dissociation energy, it has one vibrational level. Finally, the spectroscopic constants and fundamental rovibrational energy results were used to verify the stability of each system through the lifetime decomposition.

Interaction of photosynthetic pigments with single-walled carbon nanotube (15, 15): a molecular dynamics study

In this study, adsorption of photosynthetic pigments on the inner and outer surfaces of single-walled carbon nanotube (15, 15) has been investigated using molecular dynamics simulation. The binding free energy is calculated by using the linear interaction energy algorithm, that its value indicates the adsorption of all pigments is desirable in both positions. Also, despite the high similarity between each category of these pigments, their interaction with the nanotube is different, that this result can be useful to separate these pigments from one another. According to Lennard–Jones potential energy between the pigments and carbon nanotube, the interaction on the inner surface is stronger than that on the outer surface for all pigments. The chlorophylls phytol tail interacts more strongly with the nanotube compared with the porphyrin ring of chlorophylls. The ability of carotenoids to institute π–π stacking is attributed to conjugated system. Furthermore, xanthophylls due to hydrogen bonded to oxygen atom form semi-hydrogen bonds with carbon nanotube.

The extended Lennard-Jones potential energy function: A simpler model for direct-potential-fit analysis

An analytical model for the diatomic potential energy function that was recently tested as a universal function (Hajigeorgiou, 2010) has been further modified and tested as a suitable model for direct-potential-fit analysis. Applications are presented for the ground electronic states of three diatomic molecules: oxygen, carbon monoxide, and hydrogen fluoride. The adjustable parameters of the extended Lennard-Jones potential model are determined through nonlinear regression by fits to calculated rovibrational energy term values or experimental spectroscopic line positions. The model is shown to lead to reliable, compact and simple representations for the potential energy functions of these systems and could therefore be classified as a suitable and attractive model for direct-potential-fit analysis.

Molecular dynamics simulations of momentum and thermal diffusion properties of near-critical argon along isobars

Three basic diffusion properties of argon – shear viscosity, bulk viscosity and thermal conductivity – were studied in the neighborhood of the critical point using molecular dynamics (MD) and the Lennard-Jones potential energy function. MD simulations were performed along the 1.0Pc and 1.2Pc isobars. Green-Kubo relations and a Lennard-Jones pair potential were used. Four different sets of Lennard-Jones parameters were used. A comparison of computed shear viscosity and thermal conductivity values with data available from the National Institute of Standards and Technology (NIST) displayed a good agreement. Results for bulk viscosity indicated that values of this property cannot be neglected in this thermodynamic region, a result that violates the traditional and much-assumed Stokes hypothesis in classical fluid mechanics. Furthermore, it was shown that in the neighborhood of the critical region the bulk viscosity can have larger values than the shear viscosity.

Nonlinear resonances of a single-wall carbon nanotube cantilever

The dynamics of an electrostatically actuated carbon nanotube (CNT) cantilever are discussed by theoretical and numerical approaches. Electrostatic and intermolecular forces between the single-walled CNT and a graphene electrode are considered. The CNT cantilever is analyzed by the Euler–Bernoulli beam theory, including its geometric and inertial nonlinearities, and a one-mode projection based on the Galerkin approximation and numerical integration. Static pull-in and pull-out behaviors are adequately represented by an asymmetric two-well potential with the total potential energy consisting of the CNT elastic energy, electrostatic energy, and the Lennard-Jones potential energy. Nonlinear dynamics of the cantilever are simulated under DC and AC voltage excitations and examined in the frequency and time domains. Under AC-only excitation, a superharmonic resonance of order 2 occurs near half of the primary frequency. Under both DC and AC loads, the cantilever exhibits linear and nonlinear primary and secondary resonances depending on the strength of the excitation voltages. In addition, the cantilever has dynamic instabilities such as periodic or chaotic tapping motions, with a variation of excitation frequency at the resonance branches. High electrostatic excitation leads to complex nonlinear responses such as softening, multiple stability changes at saddle nodes, or period-doubling bifurcation points in the primary and secondary resonance branches.

Prediction of transport properties of CO2-N2 binary mixtures via the inversion of reduced-viscosity collision integrals

In the present study, the main purpose is to extract information about the effective intermolecular potential energy function for binary mixture of nitrogen and carbon dioxide by the usage of a direct inversion of the experimentally reduced viscosity and second virial coefficient data and then to reproduce the dilute gas transport properties from the inverted potential energy. The Lennard-Jones (12, 6) potential energy function has been employed as the initial potential model required by the inversion method. The MSV potential obtained in this way is in reasonable agreement with the independently known Co2-N2 potential energy function. Using the inverted pair potential energies, the Chapman-Enskog scheme is employed to calculate transport properties of CO2-N2 in a wide composition and temperature range. The close agreement between the predicted values and the literature results of transport properties demonstrate the predictive power of the inversion scheme.

Macroscopic Expressions of Molecular Adiabatic Compressibility of Methyl and Ethyl Caprate under High Pressure and High Temperature

The molecular compressibility, which is a macroscopic quantity to reveal the microcompressibility by additivity of molecular constitutions, is considered as a fixed value for specific organic liquids. In this study, we introduced two calculated expressions of molecular adiabatic compressibility to demonstrate its pressure and temperature dependency. The first one was developed from Wada’s constant expression based on experimental data of density and sound velocity. Secondly, by introducing the 2D fitting expressions and their partial derivative of pressure and temperature, molecular compressibility dependency was analyzed further, and a 3D fitting expression was obtained from the calculated data of the first one. The third was derived with introducing the pressure and temperature correction factors based on analogy to Lennard-Jones potential function and energy equipartition theorem. In wide range of temperatures(293<T/K<393)and pressures(0.1<P/MPa<210), which represent the typical values used in dynamic injection process for diesel engines, the calculated results consistency of three formulas demonstrated their effectiveness with the maximum 0.5384% OARD; meanwhile, the dependency on pressure and temperature of molecular compressibility was certified.

Dynamic Swarm Artificial Bee Colony Algorithm

Artificial Bee Colony (ABC) optimization algorithm is relatively a simple and recent population based probabilistic approach for global optimization. ABC has been outperformed over some Nature Inspired Algorithms (NIAs) when tested over test problems as well as real world optimization problems. This paper presents an attempt to modify ABC to make it less susceptible to stick at local optima and computationally efficient. In the case of local convergence, addition of some external potential solutions may help the swarm to get out of the local valley and if the algorithm is taking too much time to converge then deletion of some swarm members may help to speed up the convergence. Therefore, in this paper a dynamic swarm size strategy in ABC is proposed. The proposed strategy is named as Dynamic Swarm Artificial Bee Colony algorithm (DSABC). To show the performance of DSABC, it is tested over 16 global optimization problems of different complexities and a popular real world optimization problem namely Lennard-Jones potential energy minimization problem. The simulation results show that the proposed strategies outperformed than the basic ABC and three recent variants of ABC, namely, the Gbest-Guided ABC, Best-So-Far ABC and Modified ABC.

FORCE DISTRIBUTION AND OFFSET CONFIGURATION FOR CARBON NANOTUBES

In this study, a novel semi-analytical approach is presented to evaluate the preferred position of an offset inner single-walled carbon nanotube (SWCNT) with reference to the cross-section of outer one. Moreover, on the basis of the continuum method utilized together with Lennard-Jones potential function, suction energy and acceptance condition for a SWCNT entering the outer one are investigated. Using netting analysis, the optimum configuration is determined to minimize the potential energy. To obtain the nature of interaction force, a universal potential curve is presented for an offset inner tube entering various semi-infinite outer ones. Lastly, based on the direct method, the mechanics of multi-walled carbon nanotubes (MWCNT) is investigated.

Vibrations of single- and double-walled carbon nanotubes with layerwise boundary conditions: A molecular dynamics study

In the present work, the vibration characteristics of single- and double-walled carbon nanotubes under various layerwise boundary conditions at different lengths are investigated. This is accomplished by the use of molecular dynamics simulations based on the Tersoff-Brenner and Lennard-Jones potential energy functions. The effects of initial tensile and compressive strains on the resonant frequency of carbon nanotubes are also taken into consideration. From the results generated, it is observed that the natural frequency of carbon nanotubes is strongly dependent on their boundary conditions especially when tubes are shorter in length. The natural frequency and its dependence on tube end conditions reduce by increasing the tube length. The natural frequency of DWCNTs lies between those of the constituent inner and outer SWCNTs and is nearer to those of the outer one. It is further observed that the natural frequency is highly sensitive to tensile and compressive strains. The frequency shift occurring in the presence of small initial strains is positive for tensile strains and negative for compressive strains. The results obtained provide valuable information for calibrating the small scaling parameter of the nonlocal models for the vibration problem of carbon nanotubes.

A perturbed hard-sphere equation of state for liquid metals

A perturbed hard-sphere equation of state, developed previously for liquid alkali metals and liquid refractory metals, has been applied for PVT calculation of some pure liquid metals including alkaline earth metals, tin, lead, antimony, bismuth, and rubidium over a wide range of temperatures and pressures. Two temperature-dependent parameters appear in the equation of state, which are universal functions of the reduced temperature, i.e. two scale parameters are sufficient to calculate the temperature-dependent parameters. The scaling parameters can be easily obtained by employing a corresponding-states principle based on a Lennard-Jones potential energy function. Employing the present equation of state, the liquid densities of aforementioned metals at temperatures ranging from the melting point to 2000 K and at pressures ranging from vapour pressure up to 40,000 bar have been calculated and compared with experimental data. The average absolute deviation in predicted densities compared with experimental data is 1.54%.