Molecular Dynamics Simulation Study of Cavitation in Silica

Abstract

This is the synopsis of the dissertation titled, Molecular Dynamics Simulation Study of Cavitation in Silica, delivered by Mayank Sharma of the Physics Department, Indian Institute of Technology Roorkee, Uttarakhand- 247667. Cavitation is a process that can cause erosion of solid surfaces, reduce pump performance and cause vibration. Despite its negative effects, cavitation has been found to be useful in different areas, such as wastewater treatment, medical applications, and drug delivery. Recently, researchers have explored the potential of using porous silica-based materials as an alternative to graphite anodes in Li-ion batteries to improve energy storage. Silica is a widely used material, found abundantly in nature, and has diverse applications in industries such as glass and ceramics. In this context, our goal is to better understand cavitation in amorphous silica. This study aims to understand the behaviour of amorphous silica in its mechanically unstable region on the phase diagram. We performed NVT molecular dynamics simulation with the VSP-BKS force field (modified BKS potential) using LAMMPS software. The cavitation phenomenon was observed for the state points lying in the highly negative pressure regions (metastable states). We implemented serial and parallel codes to compute quantities like radial distribution function and local density. A detection mechanism to confirm the presence of cavities in the sample is given based on analysing RDF, potential energy, pressure and local density. We also investigated the system size (N) dependence of cavitation, with the probability of cavitation increasing as the system size is increased. The simulation time was fixed (from mean square displace ments calculations) along with system size (N = 216000) for further work. Volume expansion protocol was implemented in the simulation to observe the ‘onset points’ of cavitation, and hence we produced a cavitation line on the density-temperature phase diagram of silica for two different volume expansion rates of the simulation box.