Multiparticle Interactions Research Articles

Study of Raman Scattering of Light in Liquid Arenes and Their Halogen-Substituted ones in the Low-Frequency Region of the Spectrum

Purpose. Investigation of Raman scattering of light in liquid arenas and their halogenated ones in the low-frequency range of the spectrum, taking into account the clustering processes in their structure.Methods. Raman spectroscopy methods were used, as well as a modeling method using cluster representations of the structure of liquids. Raman spectra of light in the low-frequency range from 17 to 500 cm–1 were obtained using a LabRAM HR Evolution spectrometer at room temperature (23°C).Results. The analysis of theoretical and experimental work on the properties of dimeric configurations of benzene and on the effect of clustering processes in substances on their IR and Raman spectra is carried out. Low-frequency Raman spectra of liquid benzene, o-xylene, ethylbenzene, fluorobenzene, chlorobenzene, brombenzene, toluene, o-fluorotoluene, m-fluorotoluene, p-fluorotoluene, o-chlorotoluene, m-chlorotoluene, p-chlorotoluene, 2,4-dichlorotoluene, 2,6-dichlorotoluene were obtained. The model of formation and disintegration of cluster formations has been tested. Formulas have been obtained for estimating the minimum frequency of libration oscillations of the ωmin dimer formation in the cluster structure and the position of the maxima of spectral bands in the low-frequency region of the Raman spectrum, depending on the number of particles included in the cluster formations. The theoretical results obtained by ωmin are in satisfactory agreement with the experimental data within the total error.The proposed model makes it possible to predict the position of some spectral bands of the Raman spectrum. The presence of other spectral bands is obviously related to the multiparticle interaction in the cluster structure and requires additional research.Conclusion. The proposed model of formation and decay of cluster formations and the relations following from it allow us to estimate the value of the minimum frequency in the low-frequency range of the Raman spectrum of liquid arenes and their halogenated ones from the known values of the enthalpy of formation and the moment of inertia of the dimer. Conversely, using known values of the minimum frequency, the values of the enthalpy of formation and the moment of inertia of the dimer can be estimated without resorting to complex quantum mechanical calculations.

Dissipative dynamics for infinite lattice systems

We study dissipative dynamics constructed by means of non-commutative Dirichlet forms for various lattice systems with multiparticle interactions associated to CCR algebras. We give a number of explicit examples of such models. Using an idea of quasi-invariance of a state, we show how one can construct unitary representations of various groups. Moreover in models with locally conserved quantities associated to an infinite lattice we show that there is no spectral gap and the corresponding dissipative dynamics decay to equilibrium polynomially in time.

Coverage-Dependent Site-Specific Placement and Correlated Diffusion of Atomic Oxygen on Moiré-Patterned Graphene on Ru(0001).

Nano-periodic arrays of atomic oxygen are visualized on epitaxial graphene on Ru(0001) via STM following supersonic beam exposure to non-equilibrium fluxes of atomic oxygen. Self-organization of atomic oxygen on graphene is directed by the intrinsic moiré pattern of the ruthenium-graphene interface. Atom-resolved STM imaging reveals the richness of multiparticle interactions, leading to correlated atomic diffusion and placement. Pair-distribution functions demonstrate that repulsive oxygen-oxygen interactions play an increasingly important role in the site specificity and diffusivity of atomic oxygen on the moiré lattice with increasing coverage. Atomic visualization shows the number of oxygen atoms in a local region changes overall diffusion rates and promotes the correlated motion of oxygen atoms. Understanding the site specificity of oxygen adsorption and diffusive behavior of atomic oxygen on epitaxial graphene on Ru(0001) provides insight for both the synthesis and stability of moiré-templated two-dimensional materials which show promise as platforms for next-generation quantum materials and catalysts.

Co-assembly of cellulose nanocrystals and gold nanorods: insights from molecular dynamics modelling.

A coarse-grained molecular dynamics model is developed to explore the co-assembly of cellulose nanocrystals (CNCs) and gold nanorods (AuNRs) under sedimentation conditions with varying volumetric concentration and particle-size ratios. Simulations and statistical analysis reveal a noticable preferential attachment of AuNRs on the surface of CNC clusters as the solid fraction of AuNRs was increased when the volumetric fraction of the AuNRs was low. Density-driven self-assembly under sedimentation forces is primarily driven by the AuNRs. This shift in the dominant mechanism from CNCs to AuNRs reveals the limits of multi-particle interactions and formation of ordered structures in binary particle systems. The fundamental insights provided in this work into the self-assembly process in complex particle systems are valuable for the design and control of the physical conditions to achieve desired ordered structures.

Near-field thermal emission from metasurfaces constructed of SiC ellipsoidal particles

We model near-field thermal emission from metasurfaces structured as two-dimensional arrays of ellipsoidal SiC particles. The modeling approach is developed from fluctuational electrodynamics and is applicable to systems of ellipsoidal particles within the dipole limit. In all simulations, the radial lengths of particles are restricted to the range of 10–100 nm, and interparticle spacing is constrained to at least three times the particle characteristic length. The orientation and dimensions of constituent ellipsoidal particles are varied to tune localized surface phonon resonances and control the near-field energy density above metasurfaces. Results show that particle orientation can be used to regulate the relative magnitude of resonances in the energy density, and particle dimensions may be changed to adjust the frequency of these resonances within the Reststrahlen band. Metasurfaces constructed from particles with randomized dimensions display comparatively broadband thermal emission rather than the three distinct resonances seen in metasurfaces made with ellipsoidal particles of equivalent dimensions. When the interparticle spacing in a metasurface exceeds about three times the particle characteristic length, the spectral energy density above the metasurface is dominated by individual particle self-interaction and can be approximated as a linear combination of single-particle spectra. When interparticle spacing is at the lower limit of three times the characteristic length, however, multiparticle interaction effects increase and the spectral energy density above a metasurface deviates from that of single particles. This work provides guidance for designing all-dielectric, particle-based metasurfaces with desired near-field thermal emission spectra, such as thermal switches.

Inertial effects in sedimenting suspensions of solid spheres in a liquid

Particle-resolved Direct Numerical Simulations have been performed on the gravitational settling of mono-disperse solid spheres in a viscous fluid and triply periodic domain. In a comprehensive study, the bulk solid volume concentration was varied from ϕ=0.5 to 30%. To study the effect of inertia, three different Galileo numbers were considered in the inertial regime, Ga=144, 178 and 210, for which a single settling sphere exhibits distinctly different wake and path characteristics. The particle/fluid mass density ratio was fixed at 1.5. We find that for ϕ=2−30% the suspension microstructure and dynamics depend predominantly on the bulk concentration. In qualitative agreement with previous studies in literature, three different sedimentation regimes can be distinguished: (1) the dilute concentration regime for ϕ≲2% with preferential settling of particles in vertical trains, (2) the moderate concentration regime for 2%≲ϕ≲10% with preferential settling of particles in horizontal pairs with an interparticle distance of ∼ 1.5 particle diameters, and (3) the dense concentration regime for ϕ≳10% with a nearly random (“hard-sphere”) distribution of the particles in space. The clustering of particles is dictated by, respectively, trapping of particles in the wake of other particles, a drafting–kissing–tumbling (DKT) instability by which two vertically aligned particles quickly reorient themselves into a horizontally aligned particle pair, and short-range multiparticle interactions through viscous lubrication and to a lesser extent collisions between particles. In all cases, hindered settling at a reduced speed is observed as compared to a single settling sphere. The well-known Richardson–Zaki relation for the mean sedimentation velocity appears valid only for the dense concentration regime. We provide ample evidence that in the dense regime the characteristic velocity and time scales of particle motion are proportional to gDp and Dp/g, respectively, with g the gravitational acceleration and Dp the particle diameter. We also observe an ω−3 scaling of the particle velocity spectra for ωDp/g≳0.4 and we propose a model to explain this scaling behavior, based on the inertial response of the particles to small-scale flow perturbations. Kinematic waves, i.e., vertically propagating plane waves in the local concentration field, are observed in all cases, though unrelated particle motions are responsible for significant loss of the spatio-temporal coherence of the waves. The wave speed was determined from repeated space–time autocorrelations of the local concentration field and appears in reasonable agreement with Kynch sedimentation theory using the Richardson–Zaki relation. The passage of kinematic waves causes perturbations in the particle velocity at a frequency that matches well with peak frequencies in the particle velocity spectra for concentrations up to ϕ≈10%. The time-lagged cross-correlation of the vertical and horizontal particle velocity suggests that kinematic waves may trigger DKT instabilities, while conversely DKT instabilities may be responsible for the onset of kinematic waves. Finally, we suggest that obstruction and perturbation of the particle wake by neighboring particles could offer an explanation for the small influence of the Galileo number on the suspension behavior for ϕ=2−30%.

Enhanced radiative heat transfer via the coupling of multi-particle interactions with combined surface models

Radiative heat transfer (RHT) has been playing a pivotal role in the study of all length scales from macroscopic to microscopic. This work aims to theoretically enhance the RHT between nanoparticles in multi-particle and slab systems. The results show that the strong coupling between the multi-particle interactions and the combined slab surface modes including transmission and reflection can significantly enhance the inter-particle RHT at a proper slab thickness, and the maximum amplification ratio can reach up to two orders of magnitude. For larger thicknesses of the slab, the RHT decreases due to the weakening of coupled evanescent models. In addition, we show that adding graphene sheets to both sides of the middle slab produces a surface hybrid model, which can regulate the coupling properties of the multi-particle and slab by changing the chemical potential of graphene. When the resonance frequency of nanoparticles is higher than that of the slab model, the RHT between the particles at both ends increases. Instead, the conclusion is the opposite. This work may exhibit potential applications for enhancing, guiding, and regulating contactless energy management in complex many-body systems at mesoscopic scales.

High-order pump-probe and high-order two-dimensional electronic spectroscopy on the example of squaraine oligomers.

Time-resolved spectroscopy is commonly used to study diverse phenomena in chemistry, biology, and physics. Pump-probe experiments and coherent two-dimensional (2D) spectroscopy have resolved site-to-site energy transfer, visualized electronic couplings, and much more. In both techniques, the lowest-order signal, in a perturbative expansion of the polarization, is of third order in the electric field, which we call a one-quantum (1Q) signal because in 2D spectroscopy it oscillates in the coherence time with the excitation frequency. There is also a two-quantum (2Q) signal that oscillates in the coherence time at twice the fundamental frequency and is fifth order in the electric field. We demonstrate that the appearance of the 2Q signal guarantees that the 1Q signal is contaminated by non-negligible fifth-order interactions. We derive an analytical connection between an nQ signal and (2n + 1)th-order contaminations of an rQ (with r < n) signal by studying Feynman diagrams of all contributions. We demonstrate that by performing partial integrations along the excitation axis in 2D spectra, we can obtain clean rQ signals free of higher-order artifacts. We exemplify the technique using optical 2D spectroscopy on squaraine oligomers, showing clean extraction of the third-order signal. We further demonstrate the analytical connection with higher-order pump-probe spectroscopy and compare both techniques experimentally. Our approach demonstrates the full power of higher-order pump-probe and 2D spectroscopy to investigate multi-particle interactions in coupled systems.

Collective Excitation in High-Energy Nuclear Collisions—In Memory of Professor Lianshou Liu

We celebrate the legacies of our friend and mentor Professor Lianshou Liu who was one of the pioneers for the phenomenology of multi-particle interactions and initiated the physics of relativistic heavy-ion collisions in China. In this article, we discuss some of the recent exciting experimental observations on the collective phenomena including collectivity, chirality, criticality, strangeness production, and thermal equilibrium in high-energy nuclear collisions. Future directions, especially the physics at high baryon density, will be discussed with a focus on the first-order phase boundary and hyperon–nucleon interactions.

Онтологии и физические аналоги двухчастичных внутрисистемных взаимодействий по моделям дублетов

Open systems (natural, social, anthropogenic, cyber-physic, and technical ones) are initially given in actual states by their empirical descriptions, obtained from huge amount of retrospective multimodal heterogeneous empirical data. At the level of fact, the empirical descriptions contain hundreds and thousands of indicators and represent such systems at their natural scales and real complexity. Furthermore, knowledge about systems’ ontology is represented at the level of sense, knowledge whose fullness and completeness are investigated and proven. At the level of ontological knowledge, the system’s reconstructions are obtained «in parts» (in eigen qualities). And, to build reconstruction of system’s states as a whole, such system reconstructions «in parts» need to be complemented by models of two-particle, three-particle, and multi-particle interactions between eigen system qualities. Ontologies of all kinds of doublets (models of two-particle interactions named SIM, SWI, MIX, SEP, ABS, DIV) are obtained and investigated in this paper. Each such kind of model possesses discovered types and forms. And, for them, such states are revealed whose attributes of orientation, tension, and “charge” level are agreed upon values. These doublets states attributed in such a way possess analogues represented by states of physical science objects exhibiting effects of deformation field as well as electric and magnetic fields that cause «multispecies» variability of open systems.

Long-range Multiparticle Interactions Induced by Neutrino Exchange in Neutron Star Matter

Forces with a large radius of interaction can have a significant impact on the equation of state of matter. Low-mass neutrinos generate a long-range potential due to the exchange of neutrino pairs. We discuss a possible relationship between the neutrino masses, which determine the interaction radius of the neutrino-pair exchange potential, and the equation of state of neutron matter. Contrary to previous statements, the thermodynamic potential, when decomposed into the number of neutrino interactions, vanishes in any decomposition order, except for the interaction of two neutrons. In the one-loop approximation, long-range multiparticle neutrino interactions are stable in the infrared region for all neutrino masses and do not affect the equation of state of neutron matter or the stability of neutron stars.

Statistical theory of individual activity coefficients of electrolytes including multiple ionic charges

In previous work we developed a new statistical method for calculating the individual activities of ions including the association of ions. Here we study multi-particle electrostatic interactions connected within higher cluster integrals and identify the ionization constants of the mass action law of associating ion clusters. In contrast to Bjerrum and Fuoss, our concept of association is not based on spatial criteria, but instead on the strength of interaction measured in powers of the Bjerrum parameter (e2/D0kBTa; a is contact) and defined by asymptotic properties of the cluster integrals. For ion pair formation our mass action constant is the classical counterpart of Planck's famous hydrogenic partition function. As a rule, the new association constants are smaller than traditional expressions, e.g., by Fuoss and Kraus, in the interesting regions of interaction parameters about fifty percent. Several examples including CaCl2, MgCl2, Na2SO4, K2SO4, LaCl3 and a model of seawater are studied. For several associating electrolytes and seawater, reasonable agreement with experiments and Monte Carlo results is achieved.

Thermal stability of equiatomic FePt nanoclusters of different habitus with ordered and disordered structure

In this work, the thermal stability of FePt nanoclusters of different habitus is considered using the molecular dynamics method with the multiparticle interaction potential MEAM-2NN. Three variants of determining the temperatures of structural disorder/melting of these nanoclusters are presented: by the normalised per atom total energy of clusters from temperature, with approximation of curves by linear sections, the intersection points of which were used to determine the disorder temperatures; the second by the mean-square displacement of atoms; the third by visualisation of cross sections of atomic planes perpendicular to the face &lt;100&gt;. It is shown that the melting of the cluster occurs layer by layer from the surface to the volume. The temperatures of structural disorder of nanoclusters determined by different methods are in good agreement with each other.

Experimental and numerical study of the effect of the channel curvature angle on inertial focusing in curvilinear microchannels

Passive cell separation methods have attracted great attention due to their superiority over the other methods stemming from their easy fabrication, precise manipulation, cost-effectiveness, sensitivity, and simplicity. The fluid inertia in these methods is the main factor that is affected by the channel design; thus, the channel design parameters should be chosen accordingly. Even though all channel design parameters are well addressed in inertial microfluidics, the curvature angle of the channel has not yet been extensively studied. In this study, three different curvilinear microchannels with curvature angles of 180°, 210°, and 270° were designed, keeping all other remaining parameters the same. The focusing ability of the fluorescent polystyrene microparticles with diameters of 1.1, 3.3, and 9.9 μm was investigated both experimentally and numerically to understand focusing efficiency affected by the curvature angle of the microchannel. The first set of experiments was to determine the effect of the channel curvature and indicated the favorable design as channel C, which showed focusing qualities of 0.85 and 0.92 for 9.9 μm particles at volumetric concentrations of 2% and 5%, respectively. The remaining set of experiments and CFD simulations were conducted to observe the interaction of 3.3 and 9.9 μm particles and reveal the distortion of the focusing line and particulate phase contours for 9.9 μm particles at the flow rates between 0.3 and 0.7 ml/min, which was further confirmed by enriched mixtures containing 1.1, 3.3, and 9.9 μm particles. The study showed that mixtures comprising low diameter particles could not satisfy the focusing criteria, which emphasized the importance of an appropriate particle size and concentration for a single focus line. On the other hand, it was shown that geometric features of the microchannel such as the hydraulic diameter and the curvature angle together with the particle size determine the focusing quality both experimentally and numerically. To sum up, the increment of the channel curvature angle is a determining factor for particle focusing, and a single focusing line was observed on the particles maintaining the focusing criteria even in many particle conditions. While the focusing quality of the particles was reduced by multi-particle interactions, they were proven to be separable achieving the appropriate concentration ratio.

Plasmon-Exciton Interaction in Perspective Hetero-Systems

Surface plasmons and excitons have been widely studied experimentally and theoretically for various material systems. However, a number of aspects require further deeper study and understanding, among which the connection of these quasi-particles occupies an important place. New physical effects arise when plasmons and excitons in nanostructures begin to be localized at certain small distances, as a result, we can talk about their coupling. Complex systems containing the excitation of plasmons and excitons, as well as their coupling, show interesting optical properties that they cannot exhibit individually. In this type of system, the plasmon enhances the coupling between the system and the external field, and the exciton controls certain spectral properties, which opens up new possibilities for tuning their optical response. The transferred energy between plasmons and excitons becomes an important factor affecting their interaction when the resonance frequency of the localized plasmon is very close to the molecular energy transition frequency. Two types of coupling can occur depending on the ratio between the strength of the coupling and the energy losses of individual components in the system, namely strong and weak. In addition to the mutual coupling between the plasmon and the exciton, their different linewidths and ability to couple to an external field provide a variety of means to tune the optical properties of hybrid systems. Thus, it enables precise control of light at the nanometer scale, opening up possibilities for new electronics and photonics applications. In this review, we highlight the features of weak and strong modes of plasmon-exciton coupling, modern trends, and perspectives in the study of hetero-systems semiconductor–metal, metal–2D material, semiconductor–molecule, etc. Semiconductor-metal hybrid nanostructures open up exciting opportunities for the study of quantum phenomena, optical processes, and multiparticle interactions and confidently lead to application in new photonics devices.

On Laser-Induced High-Order Wave Mixing and Harmonic Generation in a Graphene Quantum Dot

We present results of numerical investigations of high-order wave mixing/harmonic generation (HWM/HHG) with many-body interaction processes derived by a strong two-frequency circular laser field in a graphene quantum dot (GQD). The influence of the relative phase of such a laser field on the spectrum of high-order harmonics generated in the GQD is shown. This may allow controlling the polarization of the generated harmonics. The GQD is described by the nearest neighbor tight-binding (TB) model. The multiparticle interaction is considered in an extended Hubbard approximation. We solve quantum kinetic equations in on-site representations for charged carriers by method have already applied by us, and obtain a general formula for high-order wave mixing/harmonic generation processes in GQD. The considerable enhancement of the HWM/HHG yield due to the matching of the symmetries of the light-wave–dot system takes place for the GQD with the particular group symmetry. The analysis of obtained results confirms enough efficiency of HWM/HHG in GQDs of the triangular and hexagonal shapes with zigzag edges at certain phases of a two-frequency circular laser field.

Computational approaches to structural properties investigation of triethylammonium- and triethanolammonium-based protic ionic liquids

• Two PILs sharing the same anion were studied, that is, TEA/MsO and TEOA/MsO. • Abilities of different computational methods to study of these PIL structures are discussed. • Effects of multiparticle interactions on the structure and binding of ions are analysed. • Interionic interactions in TEOA/MsO are stronger than in TEA/MsO. • In the mesylate-based PIL the TEOA cation is in the endo-conformation. In order to conceive nature of protic ionic liquids (PILs) and reveal how the terminal hydroxyl groups in the cation affect the liquid structure we analyse the results on quantum-chemical calculations of single ion pairs of two different PILs sharing the same mesylate anion: triethylammonium-mesylate (TEA/MsO) and triethanolammonuim-mesylate (TEOA/MsO), in combination with molecular dynamics simulations. In this study, it has been revealed that in the single TEA/MsO ion pair as well as in the bulk phase, one strong short and linear (N-)H…O(-S) hydrogen bond between cation and anion is formed. In the TEOA/MsO, formation of several hydrogen bonds involving cation’s hydrogen atoms both in the NH or OH groups is possible. In addition, whereas in a single ion pair TEOA/MsO the strongest bond is (N-)H…O(-S), in the bulk phase the bond (O-)H…O(-S) becomes the strongest. Endo conformation of the TEOA cation, being typical for its isolated state, it persists both in the ion pair and in the bulk phase. However, while in the isolated ion pair no intracationic hydrogen bonds are formed, in the bulk phase formation of these bonds is highly probable.

Ubiquitous Nature of the Reduced Higher Order SVD in Tensor-Based Scientific Computing

Tensor numerical methods, based on the rank-structured tensor representation of d-variate functions and operators discretized on large n⊗d grids, are designed to provide O(dn) complexity of numerical calculations contrary to O(nd) scaling by conventional grid-based methods. However, multiple tensor operations may lead to enormous increase in the tensor ranks (curse of ranks) of the target data, making calculation intractable. Therefore, one of the most important steps in tensor calculations is the robust and efficient rank reduction procedure which should be performed many times in the course of various tensor transforms in multi-dimensional operator and function calculus. The rank reduction scheme based on the Reduced Higher Order SVD (RHOSVD) introduced by the authors, played a significant role in the development of tensor numerical methods. Here, we briefly survey the essentials of RHOSVD method and then focus on some new theoretical and computational aspects of the RHOSVD and demonstrate that this rank reduction technique constitutes the basic ingredient in tensor computations for real-life problems. In particular, the stability analysis of RHOSVD is presented. We introduce the multi-linear algebra of tensors represented in the range-separated (RS) tensor format. This allows to apply the RHOSVD rank-reduction techniques to non-regular functional data with many singularities, for example, to the rank-structured computation of the collective multi-particle interaction potentials in bio-molecular modeling, as well as to complicated composite radial functions. The new theoretical and numerical results on application of the RHOSVD in scattered data modeling are presented. We underline that RHOSVD proved to be the efficient rank reduction technique in numerous applications ranging from numerical treatment of multi-particle systems in material sciences up to a numerical solution of PDE constrained control problems in ℝd.

Room‐Temperature Observation of Near‐Intrinsic Exciton Linewidth in Monolayer WS2 (Adv. Mater. 15/2022)

Exciton Linewidth Due to strong multiparticle interactions in 2D transition metal dichalcogenides at room temperature, their homogeneous exciton linewidths are significantly broadened, degrading the quality of their excitonic mode and emission. In article number 2108721, Yuebing Zheng and co-workers achieve near-intrinsic exciton linewidth in monolayer WS2 at room temperature, approaching the theoretical limit at 0 K. A dielectric nanosphere is designed to boost the dynamic competition between exciton and trion decay channels, rebuilding the excitonic relaxation processes with suppressed exciton nonradiative recombination.

Онтологии актуальных состояний и внутрисистемных двухчастичных взаимодействий в открытых системах

Open systems (natural, social, anthropogenic, cyber-physic, and technical ones) are initially given in actual states by their empirical descriptions, obtained from huge amount of retrospective multimodal heterogeneous empirical data. At the level of fact, the empirical descriptions contain hundreds and thousands of indicators and represent such systems at their natural scales and real complexity. Furthermore, at the level of sense, open systems are represented in eigen qualities, in ideals of states of these eigen qualities, and in reconstructions of actual states – all of them are reliable and scientifically understood, are «internalized» by fact and rationally explain it, and collectively constitute knowledge about systems’ ontology, knowledge whose fullness and completeness are investigated and proven. At the level of ontological knowledge, the system’s reconstructions are obtained «in parts» (in eigen qualities). And, to build reconstruction of system’s states as a whole, such system reconstructions «in parts» need to be complemented by models of two-particle, three-particle, and multi-particle interactions between eigen system qualities. Ontologies of all kinds of doublets (models of two-particle interactions named SIM, SWI, MIX, SEP, ABS, DIV) are obtained and investigated in this paper. Each such kind of model possesses discovered types and forms. And, for them, such states are revealed whose attributes of orientation, deformation, and charge level are agreed upon values. These doublets states of the level of ontological knowledge have at the level of fact their analogues represented by states of physical science objects exhibiting effects of deformation field as well as electric and magnetic fields that cause «multispecies» variability of open systems.