Adsorption on a Spherical Colloidal Particle from a Mixture of Nanoparticles with Competing Interactions.

Adsorption of nanoparticles on a spherical colloidal particle is studied by molecular dynamics simulations. We consider a generic model for a mixture of nanoparticles with energetically favored self-assembly into alternating layers of the two components. When both components are attracted to the colloidal particle, the adsorbed nanoparticles self-assemble either into alternating parallel tori and clusters at the two poles of the colloidal particle, or into alternating spirals wrapped around the spherical surface.

Pattern Formation in Two-Component Monolayers of Particles with Competing Interactions.

Competing interactions between charged inclusions in membranes of living organisms or charged nanoparticles in near-critical mixtures can lead to self-assembly into various patterns. Motivated by these systems, we developed a simple triangular lattice model for binary mixtures of oppositely charged particles with additional short-range attraction or repulsion between like or different particles, respectively. We determined the ground state for the system in contact with a reservoir of the particles for the whole chemical potentials plane, and the structure of self-assembled conglomerates for fixed numbers of particles.

Continuous nonequilibrium transition driven by heat flow.

We discovered an out-of-equilibrium transition in the ideal gas between two walls, divided by an inner, adiabatic, movable wall. The system is driven out-of-equilibrium by supplying energy directly into the volume of the gas. At critical heat flux we have found a continuous transition to the state with a low-density, hot gas on one side of the movable wall and a dense, cold gas on the other side.

Adsorption in Mixtures with Competing Interactions.

A binary mixture of oppositely charged particles with additional short-range attraction between like particles and short-range repulsion between different ones in the neighborhood of a substrate preferentially adsorbing the first component is studied by molecular dynamics simulations. The studied thermodynamic states correspond to an approach to the gas-crystal coexistence. Dependence of the near-surface structure, adsorption and selective adsorption on the strength of the wall-particle interactions and the gas density is determined.

Self-assembly in mixtures with competing interactions.

A binary mixture of particles interacting with spherically-symmetrical potentials leading to microsegregation is studied by theory and molecular dynamics (MD) simulations. We consider spherical particles with equal diameters and volume fractions. Motivated by the mixture of oppositely charged particles with different adsorption preferences immersed in a near-critical binary solvent, we assume short-range attraction long-range repulsion for the interaction between like particles, and short-range repulsion long-range attraction for the interaction between different ones.

Flux and storage of energy in nonequilibrium stationary states.

Systems kept out of equilibrium in stationary states by an external source of energy store an energy ΔU=U-U_{0}. U_{0} is the internal energy at equilibrium state, obtained after the shutdown of energy input. We determine ΔU for two model systems: ideal gas and a Lennard-Jones fluid.

Evaporation of liquid droplets of nano- and micro-meter size as a function of molecular mass and intermolecular interactions: experiments and molecular dynamics simulations.

Transport of heat to the surface of a liquid is a limiting step in the evaporation of liquids into an inert gas. Molecular dynamics (MD) simulations of a two component Lennard-Jones (LJ) fluid revealed two modes of energy transport from a vapour to an interface of an evaporating droplet of liquid. Heat is transported according to the equation of temperature diffusion, far from the droplet of radius R.

A molecular dynamics test of the Hertz-Knudsen equation for evaporating liquids.

The precise determination of evaporation flux from liquid surfaces gives control over evaporation-driven self-assembly in soft matter systems. The Hertz-Knudsen (HK) equation is commonly used to predict evaporation flux. This equation states that the flux is proportional to the difference between the pressure in the system and the equilibrium pressure for liquid/vapor coexistence.

Communication: relative diffusion in two dimensions: breakdown of the standard diffusive model for simple liquids.

Using molecular dynamics simulations for a liquid of identical soft spheres we analyze the relative diffusion constant DΣn(r) and the self diffusion constant Dn where r is the interparticle distance and n = 2, 3 denotes the dimensionality. We demonstrate that for the periodic boundary conditions, Dn is a function of the system size and the relation: DΣn(r = L/2) ≅ 2Dn(L), where L is the length of the cubic box edge, holds both for n = 2 and 3. For n = 2 both DΣ2(r) and D2(L) increase logarithmically with its argument.

Collapse of a nanoscopic void triggered by a spherically symmetric traveling sound wave.

Molecular-dynamics simulations of the Lennard-Jones fluid (up to 10(7) atoms) are used to analyze the collapse of a nanoscopic bubble. The collapse is triggered by a traveling sound wave that forms a shock wave at the interface. The peak temperature T(max) in the focal point of the collapse is approximately ΣR(0)(a), where Σ is the surface density of energy injected at the boundary of the container of radius R(0) and α ≈ 0.

Computer investigations on the asymptotic behavior of the rate coefficient for the annihilation reaction A + A → product and the trapping reaction in three dimensions.

We have performed intensive computer simulations of the irreversible annihilation reaction: A + A → C + C and of the trapping reaction: A + B → C + B for a variety of three-dimensional fluids composed of identical spherical particles. We have found a significant difference in the asymptotic behavior of the rate coefficients for these reactions. Both the rate coefficients converge to the same value with time t going to infinity but the convergence rate is different: the O(t(-1/2)) term for the annihilation reaction is higher than the corresponding term for the trapping reaction.

Large-scale molecular dynamics verification of the Rayleigh-Plesset approximation for collapse of nanobubbles.

We report large-scale (10(7) atoms in an 85-nm-wide container) molecular dynamics simulations of collapse of nanoscopic (5-12 nm in diameter) voids in liquid argon. During the collapse the pressure on the liquid side decreases, and this decrease propagates into liquid at the speed of sound. Despite the nonuniform profile of pressure in the liquid the solutions of the Rayleigh-Plesset equation compares well to the measured evolution of the radius of the void and the velocity of the interface.

Evaporation into vacuum: Mass flux from momentum flux and the Hertz-Knudsen relation revisited.

We performed molecular dynamics simulations of liquid film evaporation into vacuum for two cases: free evaporation without external supply of energy and evaporation at constant average liquid temperature. In both cases we found that the pressure inside a liquid film was constant, while temperature decreased and density increased as a function of distance from the middle of the film. The momentum flux in the vapor far from the liquid was equal to the liquid pressure in the evaporating film.

Molecular dynamics study on the influence of quencher concentration on the reaction rate for ionic systems.

The influence of concentrations of reagents on the rate of reaction: A+B-->C+B for low density equimolar mixtures of spherically symmetric ions immersed in the Brownian medium has been investigated by performing large scale molecular dynamics simulations. The Coulomb potential of ion-ion interactions is truncated at the cutoff distance large enough to make the kinetics of the reaction independent of its value. The simulations have been performed at conditions close to that for quenching reactions for fluophores.

Heat transfer at the nanoscale: evaporation of nanodroplets.

We demonstrate using molecular dynamics simulations of the Lennard-Jones fluid that the evaporation process of nanodroplets at the nanoscale is limited by the heat transfer. The temperature is continuous at the liquid-vapor interface if the liquid/vapor density ratio is small (of the order of 10) and discontinuous otherwise. The temperature in the vapor has a scaling form T(r,t)=T[r/R(t)], where R(t) is the radius of an evaporating droplet at time t and r is the distance from its center.

The influence of interactions between reagents on the excess in the rate of quenching reaction: molecular dynamics study.

The influence of the interactions between reagents on the excess in the rate coefficient, Deltak, for the instantaneous reaction A+B-->C+B have been investigated by performing large scale molecular dynamics simulations for simple soft spheres. The simulation method has enabled us to determine the contributions to Deltak coming from A-B as well as B-B interactions. The simulations have shown that positive values of Deltak that appear both for the liquid and for the Brownian system [M.

Computer investigations on the mechanism of the influence of quencher concentration on the rate of simple bimolecular reaction.

Molecular dynamics investigations on the influence of the concentration of B (quencher) on the rate coefficient, k(t), for the reaction A+B-->C+B are continued [M. Litniewski, J. Chem.

The influence of the quencher concentration on the rate of simple bimolecular reaction: molecular dynamics study. II.

In this paper new results of the simulations [M. Litniewski, J. Chem.

The influence of the quencher concentration on the rate of simple bimolecular reaction: molecular dynamics study.

The paper presents the results of large-scale molecular dynamics simulations of the irreversible bimolecular reaction A+B --> C+B for the simple liquid composed of mechanically identical soft spheres. The systems with the total number of molecules corresponding to 10(7)-10(9) are considered. The influence of the concentration of a quencher (B) on the surviving probability of A and the reaction rate is analyzed for a wide range of the concentrations and for two significantly different reduced densities.

Kinetics of fluorescence quenching for electron transfer and for energy transfer: molecular dynamics tests for spherical molecules.

The Smoluchowski approach to description of fluorescence quenching is tested by comparing the theory with computer simulations for the case of spherical molecules. The distance dependent sink terms describing the electron transfer mechanism and the Forster model for the energy transfer are considered. It is shown that the agreement between the rate coefficient from the model and from simulations depends on the strength of the solute-solvent interactions as well as on the speed of reaction itself.