Differences in Surface Behavior of Alkali Ions in Li ₂ O ·3SiO ₂ and Na ₂ O · 3SiO ² Glasses

Abstract

The molecular dynamics computer simulation technique was used to determine the short‐time dynamics behavior and resultant structures of ions at the surface of Li 2 0·3SiO 2 and Na 2 O‐3SiO 2 glasses. Room temperature and elevated temperatures were used. Results are compared with similar studies of the K 2 O·3SiO 2 glass surface and with recent experimental ion‐scattering‐spectroscopy data. The simulations indicate that a localized surface rearrangement occurs within picoseconds after formation of the free surface, creating a surface excess of alkali in the Na (and K) case, but not in the Li case. Elevated temperatures, even for brief times, enhance the observed surface excess of Na and K. The results correspond to those obtained from the ion‐scattering‐spectroscopy studies.