Dynamics of fluids near the consolute critical point: A molecular-dynamics study of the Widom–Rowlinson mixture

Abstract

Molecular-dynamics simulations are presented for the dynamic behavior of the Widom-Rowlinson mixture [B. Widom, and J. S. Rowlinson, J. Chem. Phys. 52, 1670 (1970)] at its critical point. This model consists of two components where like species do not interact and unlike species interact via a hard-core potential. Critical exponents are obtained from a finite-size scaling analysis. The self-diffusion coefficient shows no anomalous behavior near the critical point. The shear viscosity and thermal conductivity show no divergent behavior for the system sizes considered, although there is a significant critical enhancement. The mutual diffusion coefficient, D(AB), vanishes as D(AB) approximately xi(-1.26 +/- 0.08), where xi is the correlation length. This is different from the renormalization-group (D(AB) approximately xi(-1.065)) mode coupling theory (D(AB) approximately xi(-1)) predictions. The theories and simulations can be reconciled if we assume that logarithmic corrections to scaling are important.

Anomalies of the Sound Absorption Coefficient for Binary Solutions with a Critical Stratification Temperature

“…4, but in the high-frequency interval: = 10 (1 ), 25 (2 ), 30 (3 ), 50 (4 ), 110 (5 ), and 300 MHz (6 ) in Fig. 3, c, as well as similar plots for other examined binary solutions [12,13], testify that the fluctuation part of the sound absorption coefficient is smaller than the regular part even along the critical isotherm and isoconcentrate. Therefore, our research cancels the inequality…”

“…Hence, the analysis of the experimental and literature data obtained for the sound absorption coefficient in binary or ternary solutions [12,13] showed that the considered abnormal non-universal temperature dependences are observed, if the temperature dependences of the sound absorption coefficient are different -decreasing or increasing -for the pure components of the examined solutions. This conclusion is definitely confirmed by the experimental data obtained for the temperature dependences of the sound absorption coefficient in the frequency interval ≫ ≫ 110 MHz.…”

Finite-size scaling study of dynamic critical phenomena in a vapor-liquid transition

“…On the other hand, the situation with respect to dynamics is relatively poor. Simulation studies, that helped achieving the objective for the static phenomena, gained momentum in the context of dynamic critical phenomena only recently [25][26][27][28][29][30][31][32][33][34][35][36][37][38]. Such a status is despite the fact that adequate information on the equilibrium transport phenomena is very much essential for the understanding of even nonequilibrium phenomena like the kinetics of phase transitions [9,39].…”

Finite-size scaling study of shear viscosity anomaly at liquid-liquid criticality

“…1,3,4 Due to this reason, simulation studies of the dynamic critical phenomena are very recent. [5][6][7][8][9][10][11] In the vicinity of a critical point, various static and dynamic properties exhibit power-law singularities. 1,[12][13][14] For example, in static critical phenomena, the correlation length (ξ ), the order parameter (m), and the susceptibility (χ ) behave as 1,12 …”

“…In computer simulations, reliable calculations of collective transport properties [1,3], e.g., shear (η) and bulk (ζ) viscosities, thermal diffusivity (D T ), mutual diffusivity (D AB ) in a (A + B) binary mixture, etc., are extremely difficult due to lack of self averaging [1,3,4]. Simulation studies of dynamic critical phenomena, because of this reason, have started only recently [5][6][7][8][9][10][11].…”