A DFT-Based Aspherical Ion Model for Sodium Aluminosilicate Glasses and Melts

Abstract

Na + ions play important roles on the physical and chemical properties of aluminosilicate glasses. It is known that they strongly modify the network of tetahedral SiO 4 and AlO 4 units, but the microscopic details on how they alter the local structure remain to be fully established. Here we address this issue by performing classical molecular dynamics simulations over a wide range of glasses compositions. The simulations include atomic polarization and deformation effects through the use of a DFT-parametrized aspherical ion model (AIM), which is carefully validated against experimental data (bond lengths, neutron and X-ray diffraction, and NMR spectroscopy). We show that the structure of the glasses is a subtle interplay between the nature of bridging/nonbridging oxides and the arrangement of Na + ions around them. This reflects, in particular, on the oxide instantaneous dipole moments.