Molecular Dynamics Simulations of the Structure and Properties of Low Silica Yttrium Aluminosilicate Glasses

Yttrium aluminosilicate glasses are of technological importance in photonics, nuclear waste disposal, and as a delivery vehicle for radiation therapy. Their structures are also of great interest in glass science to elucidate the principles of glass formation and structures. We provide classical molecular dynamics simulation results of a series of yttrium aluminosilicate glasses with low silica concentration. Detailed structure analyses including coordination number, pair and bond angle distributions, Si-O and Al-O network structures, and primitive ring statistics are reported. It is found that the average aluminum coordination number decreases from 4.7 to 4.2 with increasing silica content from 5 to 20 mol%, while maintaining alumina at 55 mol%. Four-coordinated aluminum ions increase from 40% to 84% in the series and the fraction of edge-sharing alumino-oxygen polyhedra decreases, indicating an increased network former role of aluminum ions with increasing silica content. Physical properties such as elastic constant, bulk modulus, Young's modulus, and Possion's ratio were calculated. The results show a decrease of bulk, Young's, and shear moduli with increasing silica and decreasing yttria contents that is in good agreement with experimental data.