Intermediate range order in silicate melts and glasses:computer simulation studies

摘要

We present the results of large scale computer simulations to discuss the structural and dynamic properties of silicate melts with the compositions (Na_2O)(2·SiO_2),(Na_2O)(20·SiO_2) and (Al_2O_3)(2·SiO_2).We show that these systems exhibit additional intermediate range orders as compared to silica (SiO_2) where the characteristic intermediate length scaes stem from the tetrahedral network structure.Furthermore we show that the sodium dynamics in the sodium silicate systems exhibits a very peculiar feature:the long-time decay of the incoherent intermediate scattering function can be described by a Kohlrausch law with a constant exponents beta for q>q_(th) whereby q_(th) is smaller than the location of the main peak in the static structure factor for the Na-Na correlations.