Numerical Simulation Of Combined Effect Of Weak Electric Field And Ions On Water Vapor Nucleation

Charged particle-induced precipitation has the advantages of low pollution,high efficiency and wide temperature and humidity window.At present,some preliminary data have been obtained in field experiments.And statistics show that the rainfall has increased significantly,but the mechanism of charged particle-induced precipitation is unclear,especially the growth law of nanoscale water droplets lacks scientific explanation.This paper is based on molecular dynamics and quantum chemistry methods to numerically simulate the nucleation process of water vapor at the molecular scale,and aims to provide a reference for revealing the mechanism of charged particle-induced precipitation.In view of the unclear factors affecting the growth of nanoscale water droplets,this paper utilizes a combination of molecular dynamics and quantum chemistry methods to study the early and mid-term growth process of water vapor molecular nucleation.First of all,this paper investigates the influence of single ion and electric field and their coupling on nucleation.It is found that ions in the early stage of nucleation can obviously promote the growth of water vapor molecular clusters,but the electric field inhibits the growth of water molecular clusters.According to quantum chemical analysis,the ion promotes the growth of water molecule clusters because it can significantly reduce the binding free energy of water molecules.The electric field inhibits the growth of water molecule clusters because the uniform electric field causes the directional movement of water molecules,which reduces the collision probability.In the mid-stage of nucleation,weak electric field promote the growth of water droplets,and the electric field of 0.1 V/nm will inhibit the growth of water droplets.Single ions have no significant effect on the growth of water droplets in the middle of nucleation.However,when the ions and the electric field work together with the water droplets,the growth rate of the water droplets increases significantly.This paper innovatively introduces the concept of"frequency distribution"to study the mechanism of single ion and electric field coupling effect on the growth of water droplets.It is found that the electric field changes the relative position of the ion in the water droplet,thus weakening the shielding of water molecules,and makes it easier for the ion to interact with free water molecules.Then,considering that there are too many ions in the water droplet,the breakage will occur.Therefore,before studying the influence of multiple ions on the growth of the water droplet,the influence of the electric field on the maximum charge of the nanometer water droplet was investigated,and the modified Rayleigh limit formula of the water droplet under the electric field was obtained.Finally,this paper investigates the effect of multiple ions and a combination of multiple ions and electric fields on water droplets.Multiple ions can significantly promote the growth of water droplets,and the growth rate increases with the number of ions.When multiple ions and electric fields work together with water droplets,both of them can promote the growth of droplets.However,due to the limit of droplet size and the number of free water molecules in the model,as the number of ions and the electric field strength gradually increase,the droplet growth rate will reach the threshold.In the research scope of this article,the growth rate of water droplets with a diameter of 3.8 nm is the fastest when the water droplet contains 4 NH₄⁺and an applied electric field is 0.1 V/nm in the relative humidity of atmosphere 95%.This paper utilizes a combination of molecular dynamics and quantum chemistry to investigate the influence of different factors on the nucleation of water molecules in the atmosphere,which provides a reference for studying the mechanism of inducing precipitation by charged particles,and has a certain degree of practicality and innovation.