Overview of Multiscale Molecular Modeling and Simulation of Silica Aerogels

Abstract

Molecular simulation has become an integral and invaluable part of Chemical Product Engineering, as it provides fundamental and indispensable insights for a rational product design. Silica aerogels are materials with exceptional properties and correspondingly broad applications whose study has benefited from this new paradigm. The complex physical/ chemical phenomena involved in their synthesis are hard to explain with experimental data alone. This document reviews relevant atomistic studies regarding silica aerogels, highlighting their contributions to the understanding of the microscopic phenomena inherent to the sol−gel process. Quantum mechanics calculations have provided a framework for investigating the mechanisms, energetics, and products of silica precursor hydrolysis and condensation reactions. Classical molecular dynamics simulations have proven to be suitable for modeling the nanoscale porous network structure of the aerogels, allowing the reliable estimation of structural, mechanical, thermal, and surface properties. Coarse graining models have allowed the extension of these studies to the mesoscale.

Theoretical Studies on the Oligomerization of Silicate Species in Basic Solution

“…Computational approaches are efficient techniques in investigating the reaction mechanisms at the atomic and molecular levels, which have been widely used in zeolite science and have provided a great quantity of valuable information about the oligomerization of silicate acids. − The pH of the reaction mixture has a great influence on the charge states of the silicate species, which would also be hardly probed accurately experimentally. Catlow et al have studied the deprotonation process of silicate clusters in both gas phase and solution using the density functional theory (DFT) method and found that the monocharged anions are readily formed, while the further deprotonation is unfavorable .…”

Molecular Modelling Guided Modulation of Molecular Shape and Charge for Design of Smart Self-Assembled Polymeric Drug Transporters

“…QM methods can provide exceptional accuracy by obtaining the electron distribution of any molecular system but with practical size limitations of few hundred atoms due to sharply rising computational cost. The MD level can capture all non-covalent interactions at atomic resolution for systems of, typically, a few hundred thousand atoms with microsecond sampling times [ 68 ]. However, many critical problems in this field still require time and length scales far beyond atomistic MD, which can be modelled by mesoscale simulations that have been appropriately parametrized using atomistic simulations of the component building blocks and interfaces.…”

Cellular Automata Modeling of Silica Aerogel Condensation Kinetics

“…In parallel with experimental research, a theoretical and numerical study is being developed, allowing prediction of aerogels’ structure, mechanical and thermal properties and the dynamics of changes in this structure. To date, most of the attention has been directed to the numerical modeling of the aerogels’ structure (the exhaustive review can be found in [ 7 ]). Furthermore, much interest was paid to the mechanical properties of aerogels [ 8 ].…”

“…The links between aerogel structures and their mechanical properties have also been analyzed utilizing hard-sphere aggregation models by Ma et al [ 11 , 12 ]. Other methods used here are coarse-grained models [ 13 , 14 , 15 ] and multiscale models [ 7 ]. The thermal properties of aerogels have been modeled through, e.g., atomistic simulations [ 16 ].…”