title: Force Field and a Surface Model Database for Silica to Simulate Interfacial Properties in Atomic Resolution
author: Fateme S. Emami
description: Silica nanostructures find applications in drug delivery, catalysis, and composites, however, understanding of the surface chemistry, aqueous interfaces, and biomolecule recognition remain difficult using current imaging techniques and spectroscopy. A silica force field is introduced that resolves numerous shortcomings of prior silica force fields over the last 30 years and reduces uncertainties in computed interfacial properties relative to experiment from several 100% to less than 5%. In addition, a silica surface model database is introduced for the full range of variable surface chemistry and pH (Q2, Q3, Q4 environments with adjustable degree of ionization) that have shown to determine selective molecular recognition. The force field enables accurate computational predictions of aqueous interfacial properties of all types of silica, which is substantiated by extensive comparisons to experimental measurements. The parameters are integrated into multiple force fields for broad applicability to biomolecules, polymers, and inorganic materials (AMBER, CHARMM, COMPASS, CVFF, PCFF, INTERFACE force fields). We also explain mechanistic details of molecular adsorption of water vapor, as well as significant variations in the amount and dissociation depth of superficial cations at silica–water interfaces that correlate with ζ-potential measurements and create a wide range of aqueous environments for adsorption and self-assembly of complex molecules. The systematic analysis of binding conformations and adsorption free energies of distinct peptides to silica surfaces will be reported separately in a companion paper. The models aid to understand and design silica nanomaterials in 3D atomic resolution and are extendable to chemical reactions.