Two-step melting of the Weeks-Chandler-Anderson system in two dimensions

We present a detailed numerical simulation study of a two-dimensional system of particles interacting via the Weeks-Chandler-Anderson potential, the repulsive part of the Lennard-Jones potential. With the reduction of density,...

Thermodynamics and Fluctuations-Correlations of Conserved Charges in a Hadron Resonance Gas Model with Attractive and Repulsive Interaction within S-Matrix Formalism

We have extended the hadron resonance gas (HRG) model by including the effect of both attractive and repulsive interaction in the scattering matrix (S-matrix) formalism. The attractive part of the interaction is calculated using K-matrix formalism while the repulsive part is included by fitting to experimental phase shifts. We have calculated various thermodynamics quantities like pressure, energy density, entropy density etc. A good agreement between our calculations and the hadronic phase of the lattice QCD (LQCD) simulations is observed. We have also calculated fluctuations and correlations for various conserved charges like baryon, strangeness and electric charge. In the present model, χ B 2 , χ B S 11 and C B S agree well with the LQCD data.

Quantitative determination of pairing interactions for high-temperature superconductivity in cuprates

A profound problem in modern condensed matter physics is discovering and understanding the nature of fluctuations and their coupling to fermions in cuprates, which lead to high-temperature superconductivity and the invariably associated strange metal state. We report the quantitative determination of normal and pairing self-energies, made possible by laser-based angle-resolved photoemission measurements of unprecedented accuracy and stability. Through a precise inversion procedure, both the effective interactions in the attractive d-wave symmetry and the repulsive part in the full symmetry are determined. The latter is nearly angle-independent. Near Tc, both interactions are nearly independent of frequency and have almost the same magnitude over the complete energy range of up to about 0.4 eV, except for a low-energy feature at around 50 meV that is present only in the repulsive part, which has less than 10% of the total spectral weight. Well below Tc, they both change similarly, with superconductivity-induced features at low energies. Besides finding the pairing self-energy and the attractive interactions for the first time, these results expose the central paradox of the problem of high Tc: how the same frequency-independent fluctuations can dominantly scatter at angles ±π/2 in the attractive channel to give d-wave pairing and lead to angle-independent repulsive scattering. The experimental results are compared with available theoretical calculations based on antiferromagnetic fluctuations, the Hubbard model, and quantum-critical fluctuations of the loop-current order.

Interatomic repulsion softness directly controls the fragility of supercooled metallic melts

We present an analytic scheme to connect the fragility and viscoelasticity of metallic glasses to the effective ion–ion interaction in the metal. This is achieved by an approximation of the short-range repulsive part of the interaction, combined with nonaffine lattice dynamics to obtain analytical expressions for the shear modulus, viscosity, and fragility in terms of the ion–ion interaction. By fitting the theoretical model to experimental data, we are able to link the steepness of the interionic repulsion to the Thomas–Fermi screened Coulomb repulsion and to the Born–Mayer valence electron overlap repulsion for various alloys. The result is a simple closed-form expression for the fragility of the supercooled liquid metal in terms of few crucial atomic-scale interaction and anharmonicity parameters. In particular, a linear relationship is found between the fragility and the energy scales of both the screened Coulomb and the electron overlap repulsions. This relationship opens up opportunities to fabricate alloys with tailored thermoelasticity and fragility by rationally tuning the chemical composition of the alloy according to general principles. The analysis presented here brings a new way of looking at the link between the outer shell electronic structure of metals and metalloids and the viscoelasticity and fragility thereof.

The modified quasi-quantum treatment of rotationally inelastic NO(X)–He scattering

A quasi quantum treatment of molecular scattering to account for the softness of the repulsive part of the anisotropic atom-molecule PES.

INFLUENCE OF THE GUPTA POTENTIAL ON THE MELTING BEHAVIORS OF CLUSTERS

By using the standard microcanonical molecular-dynamics simulations, the melting behaviors of the clusters bound by Gupta potentials are investigated. The calculations indicate that these clusters can show different melting behaviors. The origins of these processes are studied. The effects of the attractive range and the repulsive part of the interatomic interaction on the melting behaviors of the clusters are compared and analyzed.

Structure and thermodynamic modelling of Pluronic L64 solutions

The aim of the present work is to model structure and thermodynamic properties of Pluronic L64 solutions (triblock copolymer with hydrophilic ends and a hydrophobic middle). We first determined the micelle size by dynamic light scattering at various temperatures. This helps to understand the particle formation mechanism in solution and the interparticle interactions by following the virial coefficient as well as its temperature dependence. Two semi-empirical intermolecular potentials were tested to predict sample properties. First, we used a pure Lennard- Jones pair potential and then we introduced the Lu and Marlow (LM) contribution in its repulsive part. All quantities of interest were computed using the integral equation scheme with hybridized mean spherical approximation. We found that the LM contribution corrects structure and thermodynamic properties of the system by taking into account the effect of particle size.

GIBBS FREE ENERGY OF A SYSTEM OF TWO HIGHLY CHARGED PLATES IMMERSED IN AN ELECTROLYTE

The Gibbs free energy of two highly charged plates immersed in an electrolyte solution in a finite container is investigated using mean field theory. Adiabatic potential of the charged plates, which is derived from the Gibbs free energy, has a long-range weak attractive part and medium range strong repulsive part under the Dirichlet boundary condition. From comparison with the Helmholtz adiabatic potential, it is proved that the two adiabatic potentials have qualitatively the same structure of a repulsive component and an attractive component and that the Gibbs adiabatic potential shows the stronger attractive effect.