Large well-relaxed models of vitreous silica, coordination numbers, and entropy

Abstract

A Monte Carlo method is presented for the simulation of vitreous silica. Well-relaxed networks of vitreous silica are generated containing up to 300 000 atoms. The resulting networks, quenched under the BKS potential, display smaller bond-angle variations and lower defect concentrations, as compared to networks generated with molecular dynamics. The total correlation functions T(r) of our networks are in excellent agreement with neutron scattering data, provided that thermal effects and the maximum inverse wavelength used in the experiment are included in the comparison. A procedure commonly used in experiments to obtain coordination numbers from scattering data is to fit peaks in rT(r) with a gaussian. We show that this procedure can easily produce incorrect results. Finally, we estimate the configurational entropy of vitreous silica.

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

“…Amorphous Si, Ge, or SiO 2 samples obtained by a large number of bond interchanges display a concentration of defects in far better agreement with experimental data than obtained by quenching liquid samples whose potential energy is represented by few-body potentials. 36,41 The radial distribution functions and angle probability distributions 42 obtained by this method for low-temperature amorphous samples are in good agreement with experimental data. 43,44 Until recently, models of this type have been used within a static framework or in approaches combining bond switches with energy quenches.…”

Structure of liquid and glassy methanol confined in cylindrical pores

“…26 It is sufficient to mention here that this work is based on a canonical Monte Carlo simulation of 229 molecules confined in a cylindrical pore of diameter 24Å created within a modeled silica glass. We have followed the procedure proposed by Brodka et al 5 to carve a cylindrical cavity within an equilibrium cubic structure of amorphous silica of 36Å on a side provided by Vink et al 27 In this case, nonbridging oxygens are saturated with hydrogen atoms to form surface hydroxyl groups. Although the silica matrix is subsequently kept rigid, rotation around the Si-O bond of the hydroxyl groups is allowed.…”

Structure and Properties of Amorphous Silica and Its Related Materials: Recent Developments and Future Directions

“…This drawback can be overcome by a Monte Carlo scheme using an artificial dynamics consisting of bond transpositions. Recent ly, Vink and Barkema 23) have generated large and wellrelaxed amorphous silica network composed of 300 000 atoms. It has been shown that the resultant threedimensional structure can perfectly reproduce the observed total correlation functions and interference functions.…”