Atomic properties of sodium silicate glasses obtained from the building-block method

Abstract

Atomistic simulations of $({\mathrm{Na}}_{2}\mathrm{O}{)}_{x}({\mathrm{SiO}}_{2}{)}_{1\ensuremath{-}x}$ glasses are carried out using the building-block method that uses copies of low-energy units, ``building blocks,'' to build large realistic structural models. The calculated pair-correlation functions show that the local structure of these glasses is in good agreement with diffraction experiments. The electronic density of states for the doped models reveals defects in the band gap close to the conduction tail that are localized around undercoordinated Na atoms. Thermal properties for the systems, including the thermal expansion coefficient, are studied within the quasiharmonic approximation, and compare favorably with experiment. The elastic properties of the glasses are studied by calculating bulk and shear modulus.