Molecular Dynamics Simulations on Coalescence and Non-coalescence of Conducting Droplets

Abstract

When an electric field with various strengths is applied to two adjacent conducting droplets, the droplets may completely coalesce, partially coalesce, or bounce off one another. To reveal an atom-scale mechanism of coalescence or non-coalescence, dynamic behaviors of two conducting nanodroplets at a homogeneous electric field are studied via molecular dynamics simulations in this work. The results show that there is a critical field strength and a critical cone angle above which the two droplets partially coalesce or bounce off. Charge transfer between the two droplets is observed when the droplets are brought into contact. The partial coalescence and the bounce-off of the two droplets at strong field strengths are found to be due to the high charge transfer rate, which leads to the breakup of the coalescing droplet at different locations.

Electro-coalescence of two charged droplets under constant and pulsed DC electric fields

“…Recently, Ristenpart et al [10] experimentally found that full coalescence and partial coalescence can occur for any oil/water or gas/ water system. Furthermore, MD simulations on the electrocolescence of two droplets surrounded by nitrogen gas under constant DC electric field reproduced the phenomena observed in macroscopic experiments [14]. Therefore, the nitrogen/water system is adopted in the present MD simulations for saving computational time.…”

“…The reason of the partial coalescence was speculated to be charge transfer between the two droplets [12]. Recently, Wang et al [14] have corroborated this mechanism from atomic scale via molecular dynamics (MD) simulations.…”

“…Various numerical methods have been used to study coalescence of liquid droplets, such as Lattice Boltzmann simulations [20][21][22], smoothed particle hydrodynamics [23] and molecular dynamics simulations [14]. Among these methods, molecular dynamics simulations can simulate the real process by identifying particles and following their movements through the basic laws of classical mechanics.…”

“…Among these methods, molecular dynamics simulations can simulate the real process by identifying particles and following their movements through the basic laws of classical mechanics. This method has been proven to be a powerful tool for microscopic analysis of the droplet electro-coalescence [14]. In the present work, MD simulations are carried out to investigate the coalescence dynamics of two charged droplets under pulsed DC electric field.…”

Microscopic mechanism on coalescence of the nano-droplets in present non-uniform electric field by molecular dynamics simulations

“…The water molecules are characterized by the SPC/E model with an O-H bond distance of 1.0 Å and a H-O-H angle of 109.47 • . 28 The intermolecular interactions of particles for the whole system are expressed as a combination of 12/6 Lennard-Jones and Coulombic potentials, and total potential energy can be obtained as following:…”