Microstructural analysis of liquid and amorphous SiO 2 nanoparticles

Abstract

Microstructural properties of liquid and amorphous SiO 2 nanoparticles have been investigated via molecular dynamics (MD) simulations with the interatomic potentials that have weak Coulomb interaction and Morse-type short-range interaction under non-periodic boundary conditions. Structural properties of spherical nanoparticles with different sizes of 2, 4 and 6 nm obtained at 3500 K have been studied through partial radial distribution functions (PRDFs), coordination number and bond-angle distributions, and compared with those observed in the bulk. The core and surface structures of liquid SiO 2 nanoparticles have been studied in detail. We found significant size effects on structure of nanoparticles. Calculations also show that if the size is larger than 4 nm, liquid SiO 2 nanoparticles at the temperature of 3500 K have a lightly distorted tetrahedral network structure with the mean coordination number Z Si–O≈4.0 and Z O–Si≈2.0 like those observed in the bulk. Moreover, temperature dependence of structural defects and SiO x stoichiometry in nanoparticles on cooling from the melt has been found and presented.