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This paper proposes a hybrid algorithm based on the ant colony and Physarum Polycephalum algorithms. The positive feedback mechanism is used to find the globally optimal path. The crossover and mutation operations of the genetic algorithm are introduced into the path search mechanism for the first time. The Van der Waals force is applied to the pheromone updating mechanism. Simulation results show that the improved algorithm has advantages in quality and speed of solution compared with other mainstream algorithms. This paper provides fast and accurate route methods for solving the Traveling Salesman Problem first and a delivery scheme is also presented for UAVs to realize “contactless delivery” to users in the Changchun Mingzhu District during the COVID-19 epidemic, which confirms the practicability and robustness of the algorithm.

Hypothesis High and medium internal phase Pickering emulsions stabilized with cellulose nanocrystals (CNCs) exhibited very different performance compared to their peers stabilized with a surfactant. In this paper, we ascribed the difference to the formation of hydrogen bonding and van der Waals interactions between the CNC nanoparticles on adjacent oil droplets. Experiments Rheological properties of CNC-stabilized oil-in-water medium internal phase emulsions (MIPEs, oil content = 65% v/v) and high internal phase emulsions (HIPEs, oil content = 80% v/v) were comprehensively characterized using both oscillatory and rotational tests. Findings It was found that in the MIPEs, the van der Waals and hydrogen bonding interactions dominate the emulsion properties, whereas the compact structure of oil droplets plays a more important role in the HIPEs. CNC concentration in the aqueous phase also affects the emulsion properties, especially for the HIPEs, and the results can be correlated to the stabilization mechanisms we previously reported. The information from these tests provides a much-needed guidance for the practical application of CNC-stabilized emulsions.

Single-walled carbon nanotube encapsulated in boron nitrite nanotube (SWCNT@BNNT) is a novel nanomaterial with a one-dimensional van der Waals (1D-vdW) heterostructure. In this paper, we demonstrated that the SWCNT@BNNT has an enhanced optical power tolerance compared to that of the pristine SWCNT while exhibiting an optical saturable absorption properties. Under optical power intensity of 13kW/cm2, the lifetime of the SWCNT@BNNT is found to be 2,270 times longer than SWCNT for 1% degradation in absorbance. A short-cavity mode-locked laser with a high repetition rate of 1 GHz has been realized using the SWCNT@BNNT as the saturable absorber. We have shown that the technique of fabricating nanomaterial with a 1D-vdW heterostructure can modify and enhance the optical properties of the encapsulated nanomaterials., 8 pages, 7 figures

The development of accurate force fields of energetic molecules (EM) to predict their crystal structures has been aggressively pursued in the EM research community. In this study, a non-empirical polarizable force field for energetic molecules is derived from the quantum-mechanical (QM) calculation results to well describe intermolecular interactions. We named this force field as the energetic molecule specific polarizable force field (EMS-PFF). It includes anisotropic atomic multipoles to describe the electrostatic interactions, atomic polarizability to consider the electron polarization, and standard MM2-type Buckingham dispersion-repulsion van der Waals interactions. Different from the traditional force fields by fitting some observed properties, EMS-PFF is parameterized only from the QM calculation results of energetic molecule at the MP2/6-311g(d,p) level. The QM-derived EMS-PFF is applied to optimize the 174 conversional CHNO energetic molecular crystals listed in the paper published in J. Phys. Chem. B 2004 108, 17730-17739. Our results demonstrate that EMS-PFF can better reproduce the experimental crystalline structures compared with the rigid optimization by the traditional isotropic charge-based Dreiding and COMPASS force fields. We believe that the non-empirical EMS-PFF can not only well predict the crystalline structures of the conversational CHNO energetic molecules, but also predict the crystal structures of other new high-nitrogen or full-nitrogen energetic materials.

sCO2 power cycle is the most investigated and most promising technology for replacing conventional steam cycle in CSP plants. Nevertheless, the efficiency of sCO2 power cycle is strongly penalized by high ambient temperatures which are typical of favourable CSP locations. This paper focuses on a new working fluid for power cycles which consists of CO2 blended with C6F6. The addition of C6F6 increases the fluid critical temperature allowing for a condensing cycle for ambient temperatures up to 45 °C. The calculated gross mechanical efficiency of the innovative cycle is around 42% when adopting a typical Peng Robinson equation of state with van der Waals mixing rules for a maximum operating temperature of 550 °C and a minimum cycle temperature of 51 °C. This performance varies just of ±0.1% if the prediction of the binary interaction parameter of the Peng Robinson is over- or under-estimated by 50%, but more significantly if other equations of states are adopted (up to 1% points). Moreover, a detailed analysis on the operating conditions of the cycle components highlighted that components design is affected by the adopted EoS. A sensitivity analysis is then performed to identify where the largest differences in predicting the efficiency of the cycle occur.

In this paper, we combined cavity optomechanics and quantum mechanical mechanism of van der Waals force to study the dynamic behavior of interacting bimolecules in the plasmonic localized field, and extend it to the interacting multi-molecular system. We explored how plasmonic optomechanical coupling affects the strength of intermolecular interactions. Based on our results, we propose to use optical field to modulate the intermolecular interaction potential in plasmonic cavity, which can be utilized in the enhancement of the efficiency of the molecular self-assembly process and controlling the yield of the reaction in an optical environment. This research extends molecular optomechanics from intramolecular interactions to intermolecular interactions and may has high application potential in some nanostructure synthesis.

In this paper, we explore the dynamics of a Hamiltonian system after a double van der Waals potential energy surface degenerates into a single well. The energy of the system is increased from the bottom of the potential well up to the dissociation energy, which occurs when the system becomes open. In particular, we study the bifurcations of the basic families of periodic orbits of this system as the energy increases using Lagrangian descriptors and Poincar\'e maps. We investigate the capability of Lagrangian descriptors to find periodic orbits of bifurcating families for the case of resonant, saddle-node and pitchfork bifurcations., Comment: 17 pages, 14 figures

The reaction of CH2O and NO2 plays an important role in the combustion of double-base propellants, the mechanism about the influence of PbO (SnO) on this reaction is still unclear. In this paper, we obtained the product PbCH2O2 (SnCH2O2) through DFT calculations. After wavefunction analysis (MBO, LMOs, ESP et al.), we not only deeply understood the properties of PbCH2O2 (SnCH2O2), but also realized that the introduction of heavy metals (Pb, Sn) will greatly increase the van der Waals interaction and electrostatic interaction. The calculations of reaction thermodynamics and reaction kinetics indicated that PbO (SnO) can obviously reduce the Gibbs free energy barrier and increase the reaction rate. The burning rate shown the positive correlation with the results of thermodynamics and kinetics. The analysis of the combustion residue showed that the elemental Pb (Sn) produced on the surface, which may be related to the further decomposition of PbCHO2 (SnCHO2) and also reveal a transformation cycle of PbO(SnO)-Pb(Sn). The RSFT-IR analysis of the double-base absorbent powder not only proved that the existence of PbO (SnO) could reduce the decomposition temperature of the absorbent, but also indicated that the existence of PbCH2O2 (SnCH2O2) and PbNO2 (SnNO2). Combining with the theoretical calculations and experiments, we established a reaction process about the cyclic catalysis of PbO (SnO) in double-base propellants. And more importantly, the effect of the metals with higher density and larger radius in double-base propellants deserves more attention.

Thin-film evaporation is relevant for electronics cooling, water desalination, and some energy conversion processes, and the overall performance of such applications relies on the adequate understanding of heating-induced phase-change mechanisms. Given the importance of polar compounds, such as alumina, for nanoporous membranes in water desalination, the effects of electrostatic forces on thin-film evaporation were investigated in this paper by means of molecular dynamics simulations. The influence of the electrostatic interactions was assessed by modelling the alumina-water interactions using two approaches: i) accounting for electrostatic and dispersive van der Waals (vdWs) forces between the solid and liquid atoms (LJ+Coulombic model), and ii) considering only dispersive vdWs interactions (LJ model). Additionally, a theoretical model based on the Schrage relationships was developed to compare theory and simulations. The results showed considerable differences in the evaporation rates obtained from the two interfacial models. For the LJ+Coulombic model, the liquid films were 40% thicker, and the maximum evaporation mass flux was lower than the LJ model by a factor of two. The theoretical Schrage relationships deviated from the simulation evaporation fluxes with errors of 2.2-18.1% and 24.0-57.9% for the LJ+Coulombic and LJ models, respectively. These observations suggest that the partial charges in the solid affect the evaporation behavior of water if the films are ∼5 nm or thinner. Moreover, the significant deviations in the evaporation behavior demonstrated the importance of a robust interfacial modelling approach to investigate thin-film evaporation in polar interfaces.

Today photocatalysis has been proved a vital technology to counter energy and environmental related issues. Immense research is going on to formulate a low cost, light-efficient stable photocatalyst. In this context, graphitic carbon nitride (g-C3N4), a kind of polymeric material with a mild bandgap of 2.7 eV, has shown promising results for various applications in the field of photocatalysis. Its two-dimensional structure contains one sigma and two pi bonds with a multi-layered assembly and weak interlayered van der Waals interaction. Besides its multifunctional properties, a high charge carrier recombination rate results in low quantum efficiency, limiting its photocatalytic application. Hence, customizing its photocatalytic activity has emerged as an extensive research area. To this prospect, various approaches such as concurrence with semiconductors and noble metals, doping, deploying morphology and microstructure, etc., have been implemented to modify its structure. This paper contributes a detailed review of various methodologies implemented in this regard.

The attractive part of the van der Waals potential is commonly referred to as dispersion forces. Dispersion forces are a ubiquitous phenomenon with significant implications for chemistry, biochemistry, and materials science. Admittedly, the dispersion interactions are considered “weak”. For this reason, the quantification of the dispersion forces is rather challenging. In this paper we used the DFT methodology with def2-TZVPP basis set to evaluate dispersion interactions in molecular and ionic systems. We also quantify the dispersion contributions with help of the complementary to DFT experimental methods based on thermochemical quantities: standard molar vaporization enthalpy and the ideal-gas standard molar enthalpy of formation. We used a bunch of experimental thermodynamic methods (combustion calorimetry, solution calorimetry, differential scanning calorimetry, thermogravimetry, vapour pressure determination with combined Quartz Crystal Microbalance, Knudsen method, transpiration technique, static method) to quantify the dispersion forces in molecular and ionic systems. Experimental studies have been performed on the well-chosen sets of molecular compounds (alkanes, alcohols, amines, aromatics) and ionic liquids (ammonium and phosphonium based ionic liquids). The main idea was based on the predominant view that bulky groups in molecular structures are more likely considered repulsive rather than stabilizing. In view of the fact that a delicate balance between attraction and repulsion can be quantified and rationalized, the approach developed in this work can help establish new design principles based on the conscious inclusion of dispersion as an important stabilizing factor. The ensemble of experimental techniques and quantum chemical methods (DFT with D3 dispersion correction) enabled the development of quantitative scales of the dispersion contributions and their understanding at the molecular level.

GaN-based films grown on sp3-bonded single-crystalline substrates can maintain the coherent growth character. However, exfoliating III-nitride films from these substrates proves difficult because of the strong sp3-type covalent bonds between the substrates and epilayers. The sp2-bonded two-dimensional (2D) materials exhibit hexagonal in-plane lattice arrangements and weakly bonded layers, so the GaN epilayer grown on 2D materials can be transferred onto foreign substrates with ease. In this paper, graphene is used as the inserted layer (IL) on freestanding GaN substrate and the van der Waals coherent epitaxy of GaN-based single-crystalline films on such graphene/GaN templates is investigated. Density functional theory computations are performed to probe the transmission of crystallographic information of wurtzite GaN through the graphene IL. The appropriate layer numbers of graphene IL and GaN growth temperature are optimized to demonstrate the coherent epitaxy character. Both theoretical and experimental results support that the coherent epitaxy of GaN can only be achieved by using a monolayer graphene IL, and the crystalline quality of optimized GaN film can reach the same level of that grown directly on GaN freestanding substrates.

Environmentally friendly and biodegradable insulating liquids have broad application prospects in oil-immersed power transformers. The liquid-solid interface structure of insulating oil and cellulose polymers is a critical factor that determines the performance of oil-paper composite insulation widely used in oil-immersed power transformers. In this study, the molecular details about the dynamic behaviour of hydrocarbons and ester insulating liquids on the surface of crystalline cellulose are offered. The microscopic differences between the two insulating liquid and cellulose interfaces are compared based on the density distribution, dynamic structural properties, hydrogen bonds and interaction energy analysis of the liquid-solid interface. The width of the liquid-solid interface formed by the two insulating liquids and cellulose surfaces is different. At the same time, the deflection of different cellulose surface chain lengths and the torsion angle of hydroxymethyl groups are significantly different. These phenomena are mainly attributed to the interaction between the liquid-solid interface. The interaction between the surface of the mineral oil and cellulose is based on the van der Waals effect. Natural ester double-bonded O atoms and H atoms on the cellulose surface form more hydrogen bonds or have a greater electrostatic effect. Furthermore, the adsorption energy of mineral oil on the four cellulose surfaces is basically the same, and the average value is approximately 556 kcal/mol. The (1 0 0) and (1 -1 0) cellulose surfaces have a strong adsorption capacity for natural esters, while the (1 1 0) cellulose surface has the weakest adsorption capacity for natural esters. This study provides a theoretical basis for the more scientific application of natural esters and the development of new environmentally friendly insulating materials.

In this paper we have studied Van-Der-Waals fluid system with the generalized EOS as as discussed in the recent works of Kremer, G.M [1, 4], Vardiashvili, G [2], Jantsch, R.C [3], Capozziello, S [5]. and are functions of energy density and time that are different for the three types of Van der Waals fluid which are one parameter model, two parameters model and three parameters model. We have studied the changes in the parameters for different cosmic phases. We have also investigated the thermodynamics and the stability conditions for these three models. Finally, we have resolved the finite time future singularity problems, Comment: 28 pages, 27 figures. Physica Scripta (2021)

Waste plastic, such as polyethylene (PE), and waste rubber tires, are pollutants that adversely affect the environment. Thus, the ways these materials are used are important in realizing the goals of reduced CO2 emissions and carbon neutrality. This paper investigates the fundamental properties, compatibility, and interaction mechanism of waste plastic/rubber-modified asphalt (WPRMA). Dynamic shear rheology, fluorescence microscopy, a differential scanning calorimeter, and molecular dynamic simulation software were used to evaluate the properties and mechanisms of WPRMA. The results show that the anti-rutting temperature of WPRMA with different waste plastic contents is higher than 60 °C and the optimal dosage of waste PE in WPRMA is 8%, which can enhance the high-temperature properties and compatibility of rubber-modified asphalt. The temperature can directly promote the melting and decomposition of the functional groups in WPRMA and thus must be strictly controlled during the mix production process. The interaction mechanism suggests that waste plastic can form networks and package the rubber particles in rubber-modified asphalt. The main force between waste plastic and rubber is Van der Waals force, which rarely occurs in chemical reactions.

Recently, van der Waals layered metal phosphochalcogenides with a common formula MPX3 (e.g. M = Fe, Co, Ni, Mn; X = S, Se) have attracted intensive research interest as promising candidates in optoelectronic applications because of their strong light absorption and tunable bandgap. In this paper, we report the synthesis of high-quality MnPSe3 crystals and investigate the performance of photodetector based on two-dimensional (2D) MnPSe3. The fabricated device exhibits a low dark current (0.15 pA) and a high photo-responsivity without gate bias, together with excellent photoswitching stability toward short-wavelength light. Moreover, the photoresponse properties of few-layered MnPSe3 are found to be dependent on the layer thickness, which is mainly attributed to the Schottky barrier. Our work promotes the further development of 2D MPX3 as promising photodetectors with low-power consumption.

The plasmon-phonon hybridization behavior between anisotropic phonon polaritons (APhP) of orthorhombic phase Molybdenum Trioxide (α − MoO3) and the plasmon-polaritons of Graphene layer – forming a van der Waals (vdW) heterostructure is investigated theoretically in this paper. It is found that in-plane APhP shows strong interaction with graphene plasmons lying in their close vicinity, leading to large Rabi splitting. Anisotropic behavior of biaxial MoO3 shows the polarization-dependent response with strong anti-crossing behavior at 0.55 eV and 0.3 eV of graphene’s Fermi potential for [100] and [001] crystalline directions, respectively. Numerical results reveal unusual electric field confinement for the two arms of enhanced hybrid modes: the first being confined in the graphene layer representing plasmonic-like behavior. The second shows volume confined zigzag pattern in hyperbolic MoO3. It is also found that the various plasmon-phonon hybridized modes could be wavelength tuned, simply by varying the Fermi potential of the graphene layer. The coupling response of the hybrid structure is studied analytically using the coupled oscillator model. Furthermore, we also infer upon the coupling strength and frequency splitting between the two layers with respect to their structural parameters and interlayer spacing. Our work will provide an insight into the active tunable property of hybrid van der Waals (vdW) structure for their potential application in sensors, detectors, directional spontaneous emission, as well as for the tunable control of the propagating polaritons in fields of flat dispersion where strong localization of photons can be achieved, popularly known as the flatband optics.

By introducing the general construction of Landau functional of the van der Waals system and charged AdS black hole system, we have preliminarily realized the Landau continuous phase transition theory in black hole thermodynamics. The results show that the Landau functional constructed in present paper can directly reflect the physical process of black hole phase transition. Specifically, the splitting of the global minimum of the Landau functional corresponds to the second-order phase transition of the black hole, and the transformation of the global minimum reflects the first-order phase transition of the black hole., 10 pages, 5 figures; v2:add References and some comments; v3: clarifications added; v4: match published version

Orhorhombic $\alpha$-MoO$_3$ is a layered oxide with various applications and with excellent potential to be exfoliated as a 2D ultrathin film or monolayer. In this paper, we present a first-principles computational study of its vibrational properties. Our focus is on the zone center modes which can be measured by a combination of infared and Raman spectroscopy. The polarization dependent spectra are simulated. Calculations are also performed for a monolayer form in which "double layers" of Mo$_2$O$_6$ which are weakly van der Waals bonded in the $\alpha$-structure are isolated. Shift in phonon frequencies are analyzed., Comment: 13 pages, 13 figures, 14 tables

Despite the modern level of development of computational chemistry methods and technological progress, fast and accurate determination of solvation free energy remains a huge problem for physical chemists. In this paper, we describe two computational schemes that can potentially solve this problem. We consider systems of poorly soluble drug compounds in supercritical carbon dioxide. Considering that the biggest contribution among all intermolecular interactions is made by van der Waals interactions, we model solute and solvent particles as coarse-grained ones interacting via the effective Lennard-Jones potential. The first proposed approach is based on the classical density functional theory and the second one relies on molecular dynamics simulation of the Lennard-Jones fluid. Sacrificing the precision of the molecular structure description while capturing the phase behavior of the fluid with sufficient accuracy, we propose computationally advantageous paths to obtaining the solvation free energy values with the accuracy satisfactory for engineering applications. The agreement reached between the results of such coarse-graining models and the experimental data indicates that the use of the all-atom molecular dynamic simulations for the studied systems seems to be excessive.