Size-dependent surface tension of a cylindrical nanobubble in liquid Ar

Abstract

In view of the continued disputes on the fundamental question of whether the surface tension of a vapour bubble in liquid argon increases, or decreases, or remains unchanged with the increase of curvature radius, a cylindrical vapour bubble of argon is studied by molecular dynamics simulation in this paper instead of spherical vapour bubble so as to reduce the statistical error. So far, the surface tension of the cylindrical vapour bubble has not been studied by molecular dynamics simulation in the literature. Our results show that the surface tension decreases with radius increasing. By fitting the Tolman equation with our data, the Tolman length δ = −0.6225 sigma is given under cut-off radius 2.5σ, where σ = 0.3405 nm is the diameter of an argon atom. The Tolman length of Ar being negative is affirmed and the Tolman length of Ar being approximately zero given in the literature is negated, and it is pointed out that this error is attributed to the application of the inapplicable empirical equation of state and the neglect of the difference between surface tension and an equimolar surface.

Mesoscopic Simulations of Free Surfaces of Molten Polyethylene: Brownian Dynamics/Kinetic Monte Carlo Coupled with Square Gradient Theory and Compared to Atomistic Calculations and Experiment

“…The most stable thermodynamic states of macroscopic liquids are those with the lowest surface energy and, hence, the geometries with the smallest surface area per mass of liquid. In a system with three-dimensional periodic boundary conditions, such as the ones simulated here, depending on the system dimensions and the number of particles, a liquid can form various phases such as spherical droplets (SD), cylindrical droplets (CD), free films (FF), cylindrical bubbles (CB), and spherical bubbles (SB). ,, …”

“…Finally, an automated annealing scheme is developed which aims at effecting and accelerating the transition of metastable states into thermodynamically stable ones. Depending on the polymer volume fraction in the initial configuration, melts in three-dimensionally periodic model systems simulated in the canonical ensemble can collapse into spherical and cylindrical droplets, free films, , and spherical and cylindrical bubbles . The ability of our mesoscopic simulation scheme to converge to each of these stable nanophase-separated states is assessed.…”

Atomistic and mesoscopic simulations of the interfacial dynamics of polymer melts

“…77,78,[83][84][85] Extremely thin films, however, can become unstable and collapse into energetically more favorable structures such as spherical droplets (SD), cylindrical droplets (CD), cylindrical bubbles (CB) and spherical bubbles (SB), or they may dissociate entirely into a supercritical liquid/gas phase. 77,116,117 The surface tension of complex liquids such as low 86 and high [87][88][89] molar mass alkanes, has been measured extensively in the literature via a plethora of experimental methods; some of those are the pendent drop, the Wilhelmy plate, and the sessile bubble method. MD simulations and lattice fluid models 118,119 have been employed for the estimation of the surface tensions of simple 40,41,73,74,108,120 and complex 42,43,94 fluids, in order to test the theoretical and experimental scaling laws for the surface tension as a function of the temperature 87,121 and molar mass, 86,88,89,121 and to evaluate force fields through comparisons with experimental data.…”

“…Depending on the polymer volume fraction in the initial configuration, melts in three-dimensionally periodic model systems simulated in the canonical ensemble can collapse into spherical and cylindrical droplets, 77 free films, 95,136 and spherical and cylindrical bubbles. 117 The ability of the mesoscopic simulation scheme to converge to each of these stable nanophase-separated states is assessed. This is the first time that a HPF approach [197][198][199][200][201][202][203][204][205] or a slip-link / slip-spring approach 57,62-64 is employed to describe free polymer surfaces in conjunction with a realistic EoS and square gradient theory.…”

“…In a system with three-dimensional periodic boundary conditions, such as the ones simulated here, depending on the system dimensions and the number of particles, a liquid can form various phases such as spherical droplets (SD), cylindrical droplets (CD), free films (FF), cylindrical bubbles (CB) and spherical bubbles (SB). 77,116,117 Consider a cubic system with edges of length L, subject to three-dimensional periodic boundary conditions, at temperature T, containing a liquid of mass m l and density l  , encompassing a volume l V . Making the assumption that at equilibrium the liquid is fully incompressible and thus has a constant volume irrespective of the system's geometry, we obtain the volume of the liquid as l…”