Effective Interaction Potential Research Articles

Channeling of electrons in a crossed laser field

In this article a new analytical description of the effective interaction potential for a charged particle in the field of two interfering laser beams is presented. The potential dependence on the lasers intensities, orientation and parameters of the particle entering the considered system is analyzed. It is shown for the case of arbitrary lasers crossing angle that for different values of projectile velocity the attracting potential becomes a scattering one so that the channel axes and borders interchange each other. In addition the projectile radiation spectral distribution is given and general estimations on the expected beam radiation yield are outlined.

Glass transition of charged particles in two-dimensional confinement.

The glass transition of mesoscopic charged particles in two-dimensional confinement is studied by mode-coupling theory. We consider two types of effective interactions between the particles, corresponding to two different models for the distribution of surrounding ions that are integrated out in coarse-grained descriptions. In the first model, a planar monolayer of charged particles is immersed in an unbounded isotropic bath of ions, giving rise to an isotropically screened Debye-Hückel (Yukawa)-type effective interaction. The second, experimentally more relevant system is a monolayer of negatively charged particles that levitate atop a flat horizontal electrode, as frequently encountered in laboratory experiments with complex (dusty) plasmas. A steady plasma current toward the electrode gives rise to an anisotropic effective interaction potential between the particles, with an algebraically long-ranged in-plane decay. In a comprehensive parameter scan that covers the typical range of experimentally accessible plasma conditions, we calculate and compare the mode-coupling predictions for the glass transition in both kinds of systems.

Structural Characteristics and Equation of State of the Complex Plasmas

AbstractIn this paper weakly and strongly non‐ideal plasmas are considered. In both cases the equations of state for hydrogen and dusty plasmas were studied on the basis of effective potentials. In the first case the thermodynamic properties for hydrogen plasmas were studied by the method of effective potentials taking into account quantummechanical diffraction, symmetry and screening effects. For strongly non‐ideal plasma or dusty plasma the equations of state were considered using radial distribution functions and effective interaction potential, which describes interactions of charged dust grains with dipole moments. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Effective interactions in active Brownian suspensions.

Active colloids exhibit persistent motion, which can lead to motility-induced phase separation (MIPS). However, there currently exists no microscopic theory to account for this phenomenon. We report a first-principles theory, free of fit parameters, for active spherical colloids, which shows explicitly how an effective many-body interaction potential is generated by activity and how this can rationalize MIPS. For a passively repulsive system the theory predicts phase separation and pair correlations in quantitative agreement with simulation. For an attractive system the theory shows that phase separation becomes suppressed by moderate activity, consistent with recent experiments and simulations, and suggests a mechanism for reentrant cluster formation at high activity.

The Dependence of Gamow-Teller and Isobaric Analogue Resonances on The Mean Field Parameters

The variation of Gamow-Teller and isobaric analogue resonances by the mean field parameters for double magic nuclei such as and has been searched within the framework of quasi random phase approximation (QRPA). The nucleon-nucleon effective interaction potential has been defined by considering the commutativity of the Gamow-Teller operator with the central term in the nuclear part of the total Hamiltonian. The effective interaction constant has been found from this commutativity and taken out to be a free parameter.

Gamow-Teller Strength Distributions for Some Magic Nuclei

The total Gamow-Teller strengths and their energy distributions for 96Zr, 96Sr, 54Ca, 28O, 24C and 14C have been obtained within the framework of Random Phase Approximation (RPA). The effective interaction potential has been described by considering the commutativity of the Gamow-Teller operator with the central part of the nuclear Hamiltonian.

Thermodynamical model for hydrogen storage capacity in carbon nanostructures

A simple thermodynamical model taking into account non-ideality and inhomogeneity of absorbed hydrogen molecular gas has been proposed to calculate hydrogen storage capacity in carbon nanostructures as a function of temperature and pressure. The model utilizing the effective interaction potential of the hydrogen molecule with the atoms of the considered material, is based on the experimental equation of state and a local density approximation for molecular hydrogen. We have applied the model for the search of the optimal geometry for hydrogen storage of such promising carbon materials as a set of graphene layers and bundles of carbon nanotubes. We demonstrate that the hydrogen storage capacity depends on the geometry of material and discuss the origin of this effect.

Nonthermal effects on the elastic electron–atom collision in generalized Lorentzian semiclassical plasmas: Lorentzian renormalization shielding

The Lorentzian renormalization plasma shielding effects on the elastic electron–atom collision are investigated in generalized Lorentzian semiclassical plasmas. The eikonal analysis and the effective interaction potential are employed to obtain the eikonal scattering phase shift, differential eikonal collision cross section, and total eikonal collision cross section as functions of the collision energy, impact parameter, nonthermal renormalization parameter, and spectral index of the Lorentzian plasma. It is found that the influence of Lorentzian renormalization shielding suppresses the eikonal scattering phase shift and, however, enhances the eikonal collision cross section in Lorentzian semiclassical plasmas. Additionally, the energy dependence on the total collision cross section in nonthermal plasmas is found to be more significant than that in thermal plasmas.

Investigation of Coulomb Logarithm and Relaxation Processes in Dense Plasma on the Basis of Effective Potentials

AbstractIn this paper the relaxation properties of non‐isothermal dense plasmas were studied. Based on the effective interaction potentials between particles, the Coulomb logarithm for two‐temperature non‐isothermal dense plasmas was obtained. These potentials take into consideration long‐range multi‐particle screening effects and short‐range quantum‐mechanical effects in two‐temperature plasmas. The relaxation processes in such plasmas were studied using the Coulomb logarithm. The obtained results were compared with theoretical works of other authors and with the results of molecular dynamics simulation. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Multiscale modelling of nucleosome core particle aggregation

The nucleosome core particle (NCP) is the basic building block of chromatin. Under the influence of multivalent cations, isolated mononucleosomes exhibit a rich phase behaviour forming various columnar phases with characteristic NCP–NCP stacking. NCP stacking is also a regular element of chromatin structure in vivo. Understanding the mechanism of nucleosome stacking and the conditions leading to self-assembly of NCPs is still incomplete. Due to the complexity of the system and the need to describe electrostatics properly by including the explicit mobile ions, novel modelling approaches based on coarse-grained (CG) methods at the multiscale level becomes a necessity. In this work we present a multiscale CG computer simulation approach to modelling interactions and self-assembly of solutions of NCPs induced by the presence of multivalent cations. Starting from continuum simulations including explicit three-valent cobalt(III)hexammine (CoHex3+) counterions and 20 NCPs, based on a previously developed advanced CG NCP model with one bead per amino acid and five beads per two DNA base pair unit (Fan et al 2013 PLoS One 8 e54228), we use the inverse Monte Carlo method to calculate effective interaction potentials for a ‘super-CG’ NCP model consisting of seven beads for each NCP. These interaction potentials are used in large-scale simulations of up to 5000 NCPs, modelling self-assembly induced by CoHex3+. The systems of ‘super-CG’ NCPs form a single large cluster of stacked NCPs without long-range order in agreement with experimental data for NCPs precipitated by the three-valent polyamine, spermidine3+.

Vibration–rotation interaction potential for H2O–A system

The contact transformation method is used to derive an effective interaction potential for H2O–A system. The expressions for the second order vibrational and rotational correction terms are obtained. The contributions of the third order, which take into account the Coriolis and Fermi resonances in H2O molecule, are obtained too. The matrix elements of a transformed interaction potential that are necessary for calculating the broadening parameters of H2O lines perturbed by mono-atomic gases are presented.

Conformations and effective interactions of polymer-coated nanoparticles at liquid interfaces.

We investigate conformations and effective interactions of polymer-coated nanoparticles adsorbed at a model liquid-liquid interface via molecular dynamics simulations. The polymer shells strongly deform at the interface, with the shape governed by a balance between maximizing the decrease in interfacial area between the two solvent components, minimizing unfavorable contact between polymer and solvent, and maximizing the conformational entropy of the polymers. Using potential of mean force calculations, we compute the effective interaction between the nanoparticles at the liquid-liquid interface. We find that it differs quantitatively from the bulk and is significantly affected by the length of the polymer chains and by the solvent quality. Under good solvent conditions, the effective interactions are always repulsive and soft for long chains. The repulsion range decreases as the solvent quality decreases. In particular, under poor solvent conditions, short chains may fail to induce steric repulsion, leading to a net attraction between the nanoparticles, whereas with long-enough chains the effective interaction potential may feature an additional repulsive shoulder at intermediate distances.

Considering induced dipoles in a discrete model of a polar liquid

The lattice gas model is generalized to describe the equilibrium distributions of polar solution components with allowance for Lennard-Jones and dipole-dipole potential interactions with constant and induced moments. It is shown that including induced dipoles potential results in an effective many-particle interaction potential, depending on the spatial distribution of solution components. The distributions of all solution components are calculated in a quasi-chemical approximation allowing for the spatial correlation of interacting particles. A procedure for reducing the dimensionality of a set of algebraic equations is considered, and expressions for vapor-liquid equilibrium isotherms are obtained. Expressions for the rates of elementary mono- and bimolecular chemical reactions are derived using the transition state theory in systems with induced dipoles for rapidly overcoming the activation barrier in the permanent state of solvent molecules’ atomic subsystems. Ways of considering the internal motions (vibrations, rotation, and displacements) of molecules in a polar liquid are discussed.

Effective interaction between a colloid and a soft interface near criticality.

Within mean-field theory we determine the universal scaling function for the effective force acting on a single colloid located near the interface between two coexisting liquid phases of a binary liquid mixture close to its critical consolute point. This is the first study of critical Casimir forces emerging from the confinement of a fluctuating medium by at least one shape responsive, soft interface, instead of by rigid walls only as studied previously. For this specific system, our semi-analytical calculation illustrates that knowledge of the colloid-induced, deformed shape of the interface allows one to accurately describe the effective interaction potential between the colloid and the interface. Moreover, our analysis demonstrates that the critical Casimir force involving a deformable interface is accurately described by a universal scaling function, the shape of which differs from that one for rigid walls.

Nonthermal Lorentzian wake-field effects on collision processes in complex dusty plasmas

The influence of nonthermal Lorentzian wake-field on the electron-dust grain collision is investigated in complex dusty plasmas. The Eikonal method and the effective interaction potential are applied to obtain the Eikonal scattering phase shift, the differential Eikonal collision cross section, and the total Eikonal collision cross section as functions of the collision energy, the impact parameter, the Mach number, and the spectral index of Lorentzian plasma. It is found that the nonthermal effect enhances the Eikonal scattering phase shift and, however, suppresses the Eikonal collision cross section for the electron-dust grain in Lorentzian complex dusty plasmas. It is also found that the Eikonal scattering phase shift decreases with increasing Mach number and spectral index. In addition, the Eikonal collision cross section increases with an increase of the spectral index and Mach number in Lorentzian complex dusty plasmas.

Plasma Screening Effects on Atomic Collisional Orientation in Quantum Plasmas

The quantum plasma screening effects on the atomic collisional orientation phenomena are investigated for the electron-impact excitations of the hydrogenic ion in quantum plasmas. The excitation probabilities and orientation parameter are derived as functions of the collision energy, impact-parameter, and quantum wavenumber using the semiclassical method and effective interaction potential. It is found that the influence of quantum plasma screening enhances the atomic excitation probabilities. The detailed investigations on the variation of excitation preference owing to the quantum screening effects are also presented in figures.

Renormalization plasma shielding effects on scattering entanglement fidelity in dense plasmas

The influence of renormalization plasma screening on the entanglement fidelity for the elastic electron-atom scattering is investigated in partially ionized dense hydrogen plasmas. The partial wave analysis and effective interaction potential are employed to obtain the scattering entanglement fidelity in dense hydrogen plasmas as functions of the collision energy, the Debye length, and the renormalization parameter. It is found that the renormalization plasma shielding enhances the scattering entanglement fidelity. Hence, we show that the transmission of the quantum information can be increased about 10% due to the renormalization shielding effect in dense hydrogen plasmas. It is also found that the renormalization shielding effect on the entanglement fidelity for the electron-atom collision increases with an increase of the collision energy. In addition, the renormalization shielding function increases with increasing collision energy and saturates to the unity with an increase of the Debye length.

Equation of State for a Two-Dimensional Coulomb Gas

This work develops the cluster approach proposed by L.A. Bulavin and M.N. Malomuzh to the description of the phase diagram for a two-dimensional Coulomb gas. We restrict ourselves by the ensemble of the simplest clusters – dipole pairs. The effective interaction potential of dipole pair conserving a two particle configuration integral is constructed. In order to reflect more completely the long-range interaction in the system, the third virial coefficient is taken into account. The phase diagram of the Coulomb gas is analyzed on the basis of the generalized van der Waals equation of state, whose parameters are some functions of the temperature and the density. The position of the critical point is determined in different approximations. It is shown that this problem is essentially non perturbative.

On magnon mediated Cooper pair formation in ferromagnetic superconductors

Identification of pairing mechanism leading to ferromagnetic superconductivity is one of the most challenging issues in condensed matter physics. Although different models have been proposed to explain this phenomenon, a quantitative understanding about this pairing is yet to be achieved. Using the localized-itinerant model, we find that in ferromagnetic superconducting materials both triplet pairing and singlet pairing of electrons are possible through magnon exchange depending upon whether the Debye cut off frequency of magnons is greater or lesser than the Hund's coupling (J) multiplied by average spin (S) per site. Taking into account the repulsive interaction due to the existence of paramagnons, we also find an expression for effective interaction potential between a pair of electrons with opposite spins. We apply the developed formalism in case of UGe2 and URhGe. The condition of singlet pairing is found to be fulfilled in these cases, as was previously envisaged by Suhl [Suhl, Phys. Rev. Lett. 87, 167007 (2001)]. We compute the critical temperatures of URhGe at ambient pressure and of UGe2 under different pressures for the first time through BCS equation. Thus, this work outlines a very simple way to evaluate critical temperature in case of a superconducting system. A close match with the available experimental results strongly supports our theoretical treatment.

Renormalization screening and collision-induced quantum interference in dense plasmas

The influence of renormalization screening and collision-induced quantum interference in electron-electron collisions is investigated in partially ionized dense hydrogen plasmas. The effective interaction potential with the total spin-states of the collision system is considered to obtain the differential electron-electron scattering cross section. The results show that the renormalization plasma screening effect suppresses the electron-electron scattering cross section, including the quantum interference effect, especially, except for the forward and backward scattering directions. It is also shown that the renormalization plasma screening effect on the scattering cross section decreases with increasing collision energy. However, the renormalization screening effect is found to be important for the forward directions in the scattering cross section neglecting the quantum interference effect. The variations of the renormalization screening and collision-induced quantum interference effects are also discussed.