Molecular dynamics simulation of La 2O 3–Na 2O–SiO 2 glasses. III. The driving forces of clustering

Abstract

Molecular dynamics simulations have been carried out to determine the mean force and the potential of mean force of two La ions in a soda silicate glass. The reaction coordinate starts from a well separated state where the network accommodates the high-field strength cations and then brings them together to form an La–O–La linkage that can lead to the formation of free O anions. It is found that clustering of La ions is favored, at least for dimer states. Similar calculations for the ion pairs of La–La, Na–Na and La–Na in pure silica reveal that the local molecular environments of La and Na ions are quite distinct.