Molecular dynamics simulations of silica aerogels

Abstract

Molecular dynamics (MD) simulations offer a significant advantage over experimental procedures to investigate the sol-gel reactions because they present a detailed insight into the atomic-scale phenomena that underlie the formation of the gel network. In this work, silica aerogel networks with different densities modelled using MD simulations will be presented. The Vashishta potential [1] captures the interatomic behavior, while it accounts for two- and three-body interactions between Si, O, and H atoms. Condensation reactions are simulated and the resulting water molecules are allowed to stay in the system, thus the model mimicks the synthesis of aerogels in autoclaves under high temperature and pressure. The structural evolution of the silica backbone in the network is investigated. To model the supercritical drying, the water molecules are gradually removed from the system. The resulting aerogel model systems are investigated for their structural and mechanical properties. Uniaxial tensile and compressive simulations will be presented, and properties such as their Young's modulus will be quantified. Reference [1] Vashishta et al., Physical Review B 41(17): 12197 (1990)