A new method for the determination of surface tension from molecular dynamics simulations applied to liquid droplets

For the determination of surface tension of liquid droplets by molecular dynamics simulations, the most time-consuming part is the calculation of pressure tensor in the transition layer, which makes it difficult to enhance the precision of the computation. A new method for the calculation of surface tension of liquid droplets to reduce the calculation quantity of pressure tensor in transition layer to the minimum is proposed in this paper. Two thousand particles are taken as example to show how to carry out our scheme

On the applicability of Young-Laplace equation for nanoscale liquid drops

Debates continue on the applicability of the Young-Laplace equation for droplets, vapor bubbles and gas bubbles in nanoscale. It is more meaningful to find the error range of the Young-Laplace equation in nanoscale instead of making the judgement of its applicability. To do this, for seven liquid argon drops (containing 800, 1000, 1200, 1400, 1600, 1800, or 2000 particles, respectively) at T = 78 K we determined the radius of surface of tension R (s) and the corresponding surface tension gamma (s) by molecular dynamics simulation based on the expressions of R (s) and gamma (s) in terms of the pressure distribution for droplets. Compared with the two-phase pressure difference directly obtained by MD simulation, the results show that the absolute values of relative error of two-phase pressure difference given by the Young-Laplace equation are between 0.0008 and 0.027, and the surface tension of the argon droplet increases with increasing radius of surface of tension, which supports that the Tolman length of Lennard-Jones droplets is positive and that Lennard-Jones vapor bubbles is negative. Besides, the logic error in the deduction of the expressions of the radius and the surface tension of surface of tension, and in terms of the pressure distribution for liquid drops in a certain literature is corrected

Molecular dynamics simulation of an argon cluster filled inside carbon nanotubes

The effects of the diameters of single-walled carbon nanotubes (SWCNTs) (7.83 angstrom to 27.40 angstrom) and temperature (20 K-45 K) on the equilibrium structure of an argon cluster are systematically studied by molecular dynamics simulation with consideration of the SWCNTs to be fixed. Since the diameters of SWCNTs with different chiralities increase when temperature is fixed at 20 K, the equilibrium structures of the argon cluster transform from monoatomic chains to helical and then to multishell coaxial cylinders. Chirality has almost no noticeable influence on these cylindrosymmetric structures. The effects of temperature and a non-equilibrium sudden heating process on the structures of argon clusters in SWCNTs are also studied by molecular dynamics simulation

Microscopic Expression of the Surface Tension of Nano-Scale Cylindrical Liquid and Applicability of the Laplace Equation

There is no consensus on whether the macroscopic Laplace Equation of capillarity is applicable for nanoscale systems. The microscopic expression for the radius and surface tension of the surface of tension for cylindrical liquid were deduced on Gibbs theory of capillarity. The radii and tensions of the surfaces of tension and the differences between internal and outside pressure for several argon liquid cylinders consisting of different numbers of atoms with Lennard-Jones (LJ) potential under the temperature of 90 K were obtained by combination of molecular dynamics simulation and calculation. The results suggested that Laplace equation could be applicable in nanoscale with fairly good approximation