Abstract: The coordination and bond properties of aluminium and silicon ions were discussed by means of molecular dynamics simulation. By combining KA and MATSUMIYA potentials, the results of simulations agree better with the experiments. Trend of coordination and bond properties changing along with the increasing content Al₂O₃ from 0 to 100%(mole fraction) was obtained. Average bond lengths of Si-O in these simulations are within the range of 1.60～1.63Å and become smaller from 1.63Å in sample 0 to 1.60Å in sample 9 along with increasing content of Al₂O₃. Average bond lengths of Al-O are within the range from 1.77Å in sample 1 to 1.86Å in sample 10. By analyzing therelation of CN(T) and CNSi(T) with Si/(Si+Al), it is found that Al mainly locates on the tetrahedral sites which neighbor the Si tetrahedra but avoid the Al tetrahedra while alumina content is low. Whereas when Si/(Si+Al)＜0.5, Al-octahedral units appeared and became predominant gradually. Meanwhile, Al avoidance principle can only be maintained at low alumina content. With increasing alumina, this principle would be broken gradually.

Key words:  Al₂O₃-SiO₂ melts; coordination and bond properties;  molecular dynamics simulation