Dehydroxylation and Silanization of the Surfaces of β-Cristobalite Silica:  An ab Initio Simulation

Abstract

Dehydroxylation and silanization processes on the silica surface are studied by ab initio molecular dynamics. The ( 100) and ( 111) surfaces of β-cristobalite are used as two possible models of the hydroxylated amorphous surface. The activation energy and latent heat for the dehydroxylation reactions of the (100) surface computed by constrained ab initio molecular dynamics are in reasonable agreement with experimental data on the amorphous surface. Adhesion reactions of silanes are simulated aiming at elucidating the binding mechanism of organosilanes used for instance as silica-polymer coupling agents. The simulation have provided insights on the occurrence of multiple silica-silane bonds and on the role of hydrolization of silane by physisorbed water in the adhesion on the wet surface.

Thermodynamic properties and atomistic structure of the dry amorphous silica surface from a reactive force field model

“…Theoretical and computational investigations of silica surfaces have been represented primarily by ab initio determinations of the atomic and electronic structures of ordered surfaces, [18][19][20] by force field investigations of surface vibrational properties, and by computer simulations of ordered and especially amorphous surfaces at nonzero temperature, based on empirical model potentials. Mixed quantum mechanical-molecular mechanics ͑QMMM͒ approaches have been used as well to investigate the grafting of organic molecules on the surface of dry amorphous silica.…”

“…A few molecular-dynamics simulations of silica surfaces have also been performed based on ab initio methods. 18,19,37,38 The time scale accessible to ab initio methods is 2 or 3 orders of magnitude shorter than for classical potentials and also the size scale is severely restricted, thus limiting the ability of ab initio simulation to represent amorphous surfaces. These problems, of course, are to some extent compensated by the fact that ab initio models provide a comprehensive description of ionic and covalent bondings, as well as electronic polarization and charge transfer.…”

A Perspective on Multi-scale Simulation: Toward Understanding Water-silica

“…Extensive efforts have been made to study absorption, diffusion, and penetration of water molecules on SiO 2 surfaces experimentally [7][8][9][10][11][12][13][14][15][16][17][18][19][20] and computationally [21][22][23][24][25][26][27][28][29][30][31][32][33]. These studies have yielded substantial data that enable understanding of the water-silica interaction at both macroscopic and microscopic levels.…”

Selective Electroless Silver Deposition on Graphene Edges

“…The binding energy of OH-groups is 0.8-3 eV 45 and 0.54 eV 46 respectively for SiO 2 and graphene pristine surfaces, while it is larger for defects (1.8 eV for defected graphene with Stones-Wales and vacancy defects 46 ). Therefore, we expect HCl to remove the majority of OH-groups from the graphene surface and leave silver on SiO 2 and along the graphene edges.…”