Phosphate Glasses

Phosphate glasses are one of the three most important families of glass-forming oxides. This chapter briefly introduces phosphate glasses, and then reviews over 20 years of atomistic modeling studies beginning from the 1990s. The most common modeling method has been classical molecular dynamics, and the most influential interatomic potentials are discussed in detail. Also discussed are many studies based on ab initio modeling and on reverse Monte Carlo modeling. The structures of phosphate glasses, like those of silicate glasses, are based on corner-sharing networks of tetrahedral units. Modeling results provide key insights into the relation between the glass network and the local atomic environment and distribution of modifier cations. This systematic review of modeling studies follows the major categories of phosphate glass compositions: vitreous phosphorous oxide; alkali, and alkaline earth phosphate glasses; transition metal, and rare earth phosphate glasses. While the major focus of modeling studies has been on static structure, several studies stand out for their success in modeling dynamic phenomena, including vibrational frequencies, glass transition temperatures, and ionic conductivities. Modeling studies have been motivated by key applications of phosphate glasses such as laser glasses, for vitrification of nuclear waste, and biomaterials. In the latter context, modeling studies of the notable phosphate-based glasses (PBGs), and of “Bioglass” (45S5) are touched upon. Additionally, limited work on modeling of borophosphate and phosphosilicate glasses is discussed. Due to their shorter history, and the more challenging chemistry involved, modeling studies of phosphate glasses have not yet achieved the same depth and sophistication as those of silicate glasses. Nevertheless, the work of the last three decades has established a reliable foundation for atomistic modeling to be a mainstay for the future development of phosphate glasses.