  Bioactive glasses release ions such as sodium when implanted in the human
body. However, an excess of the released ions can cause problems related to
cytotoxicity. The ion release control is considered one of the primary
challenges in developing new bioactive glasses. Here, we use molecular dynamics
simulations to investigate the effect of the density on atoms' dynamics in an
archetypal phosphosilicate bioactive system. The diffusion coefficient displays
three main regimes with increasing density. The mobility of the modifiers is
significantly affected by the increase of the density, especially Na, compared
to other elements. We use a modified Arrhenian model to access the complex
dynamic behavior of 45S5 melts and correlate it to the structural changes by
evaluating the network connectivity and pair-excess entropy. Overall, our
results present a step toward the rational design of bioactive glasses and a
key to controlling the ion release of bioactive glasses.
