Q-Species In Alkali-Disilicate Glasses

Glasses of composition M20.2Si02 (M=Li, Na, K Rb and Cs) were obtained by means of molecular dynamics simulation. The structures of these glasses were analysed with the help of Q-species distribution. The influence of alkali oxide on a decay of Q-species is monitored according to the equation 2Q(n)=Q(n-1)+Q(n+1). Equilibrium constant of this equation is defined by the relation k(n)=(Q(n-1))(Q(n+1))/(Q(n))2. It was found that k3 is decreasing in sequence Li more than Na more than K so that the decay of Q3 is preferred for smaller alkali ions. Systems with higher k3 tend to create the silicate-rich regions (abundant in Q4) and alkali-rich regions where alkali ions are spread among chain-like structures formed by Q3 units.