arXiv subjects

E. N. Tsiok

Publications and source records attributed to E. N. Tsiok.

42 records · Page 3Linked to original sources

arXiv2014

The "True" Widom Line for a Square-Well System

In the present paper we propose the van der Waals-like model, which allows a purely analytical study of fluid properties including the equation of state, phase behavior and supercritical fluctuations. We take a square-well system as an example and calculate its liquid - gas transition line and supercritical fluctuations. Employing this model allows us to calculate not only the thermodynamic response functions (isothermal compressibility $β_T$, isobaric heat capacity $C_P$, density fluctuations $ζ_T$, and thermal expansion coefficient $α_T$), but also the correlation length in the fluid $ξ$. It is shown that the bunch of extrema widens rapidly upon departure from the critical point. It seems that the Widom line defined in this way cannot be considered as a real boundary that divides the supercritical region into the gaslike and liquidlike regions. As it has been shown recently, the new dynamic line on the phase diagram in the supercritical region, namely the Frenkel line, can be used for this purpose.

cond-mat.soft↗

arXiv2013

"Liquid-gas" transition in the supercritical region: Fundamental changes in the particle dynamics

Recently, we have proposed a new dynamic line on the phase diagram in the supercritical region. Crossing this line corresponds to the radical changes of the fluid properties. Here, we focus on the dynamics of model Lennard-Jones and Soft-Sphere fluids. We show that the change of the dynamics from the liquid-like to gas-like can be established on the basis of the velocity autocorrelation function and mean-square displacement. Using the rigorous criterion, we show that the crossover of particle dynamics and key liquid properties occurs at the same line. We further show that positive sound dispersion disappears in the vicinity of this line in both kinds of systems. The dynamic line bears no relationship to the existence of the critical point. We find that the region of existence of liquid-like dynamics narrows with the increase of the exponent of the repulsive part of inter-particle potential.

cond-mat.soft↗

arXiv2013

Silica-Like Sequence of Anomalies in Core-Softened Systems

In this paper we present a simulation study of density, structural and diffusion anomalies in core-softened system introduced in our previous publications. It is well-known, that with appropriate parametrization, core-softened systems are remarkable model liquids that exhibit anomalous properties observed in tetrahedral liquids such as silica and water. It is widely believed that core-softened potentials demonstrate the water-like sequence of anomalies. We show that with increasing the depth of the attractive part of the potential the order of the region of anomalous diffusion and the regions of density and structural anomalies is inverted and have the silica-like sequence. We also show that the slope of the Widom line is negative like in water.

cond-mat.soft↗

arXiv2011

Inversion of Sequence of Diffusion and Density Anomalies in Core-Softened Systems

In this paper we present a simulation study of water-like anomalies in core-softened system introduced in our previous publications. We investigate the anomalous regions for a system with the same functional form of the potential but with different parameters and show that the order of the region of anomalous diffusion and the region of density anomaly is inverted with increasing the width of the repulsive shoulder.

cond-mat.soft↗

arXiv2011

Core-Softened System With Attraction: Trajectory Dependence of Anomalous Behavior

In the present article we carry out a molecular dynamics study of the core-softened system and show that the existence of the water-like anomalies in this system depends on the trajectory in $P-ρ-T$ space along which the behavior of the system is studied. For example, diffusion and structural anomalies are visible along isotherms as a function of density, but disappears along the isochores and isobars as a function of temperature. On the other hand, the diffusion anomaly may be seen along adiabats as a function of temperature, density and pressure. It should be noted that it may be no signature of a particular anomaly along a particular trajectory, but the anomalous region for that particular anomaly can be defined when all possible trajectories in the same space are examined (for example, signature of diffusion anomaly is evident through the crossing of different isochors. However, there is no signature of diffusion anomaly along a particular isochor). We also analyze the applicability of the Rosenfeld entropy scaling relations to this system in the regions with the water-like anomalies. It is shown that the validity of the Rosenfeld scaling relation for the diffusion coefficient also depends on the trajectory in the $P-ρ-T$ space along which the kinetic coefficients and the excess entropy are calculated.

cond-mat.soft↗

arXiv2010

Complex Phase Behavior of The System of Particles with Smooth Potential with Repulsive Shoulder and Attractive Well

We report a detailed simulation study of the phase behavior of core softened system with attractive well. Different repulsive shoulder widthes and attractive well depthes are considered which allows to monitor the influence of repulsive and attractive forces on the phase diagram of the system. Thermodynamic anomalies in the systems are also studied. It is shown that the diffusion anomaly is stabilized by small attraction.

cond-mat.soft↗