Alternative insight into aluminium-phosphate glass network from ab initio molecular dynamics simulations

Phosphate glasses are an important group of materials for wide applications. They have received attention as biomaterials, eco-fertilizers, in optoelectronic devices, waste immobilization, etc. The subject of the studies is binary Al2O3–P2O5 glass, seen by ab initio molecular dynamics simulations. In the paper, Mayer's Bond Order analysis was employed as a suitable tool to observe the changes in the network due to Al2O3 substitutions. As well as, the bonding properties across the atoms in the network, which were characterized by electron localization function. The basic structural properties of the glasses are presented. The simulations showed that oxygen atoms in [PO4] tetrahedrons create a weak covalent bond between the atoms. The interaction spreads across the whole phosphate network via bridging oxygens. Whereas, there is no such interaction between the atoms in [AlOx] polyhedrons. In the case of the Al2O3 rich glasses, there are evidence non-network oxygen atoms which influence the distribution of phosphate structural units predicted based on the O/P ratio. The possibility of estimation of the oxygens in an experiment is discussed. The atoms building the network are going to take specific values of the total bond orders and the glass network is an interplay between atoms' affinity to saturate bond orders and the glass network neutrality.