  Due to its ability to bond with living tissues upon dissolution, 45S5
bioglass and related compositions are promising materials for the replacement,
regeneration, and repair of hard tissues in the human body. However, the
details of their atomic structure remain unclear. This is partially due to the
non-equilibrium nature of glasses, as their non-crystalline structure is highly
dependent on their thermal history, namely, the cooling rate used during
quenching. Herein, using molecular dynamics (MD) simulations and magic angle
spinning nuclear magnetic resonance (MAS-NMR) spectroscopy experiments, we
investigate the structure of the nominal 45S5 bioglass composition prepared
using cooling rates ranging over several orders of magnitude. We show that the
simulations results are in very good agreement with experimental data, provided
that they are extrapolated toward lower cooling rates achieved in experiments.
These results highlight that previously reported inconsistencies between
simulations and experiments stem from the difference in cooling rate, thereby
addressing one of the longstanding questions on the structure of bioglass.
Based on these results, we demonstrate the existence of a Si--P avoidance
behavior, which may be key in controlling the bioactivity of 45S5 bioglass.
