We have used molecular dynamics (MD) simulation to investigate ionic self‐diffusivity in NaAlSi2O6 melts and glasses at pressures of 3–58 GPa and temperatures of 2500–5000 K, to evaluate the effectiveness of a two‐body potential in reproducing pressure and temperature dependence of tracer self‐diffusivities. For each species, self‐diffusivity increased with increasing temperature; with increasing pressure up to ∼15 GPa, the self‐diffusivity of O, Si, and Al increased, while mobility of Na decreased. An Arrhenian fit to self‐diffusivity data collected from simulations at temperatures above the kinetic glass transition (up to 15 GPa) gives: Species Ea Va log D* (kJ/mol) (×106m³/mol) (m²/s) Na 81±14 3.5±0.5 −6.8±0.17 Al 306±31 −5.6±1.1 −6.5±0.35 Si 294±23 −6.1±0.9 −6.9±0.26 O 302±23 −5.9±0.8 −6.6±0.26 for activation energy (Ea) and activation volume (Va). The MD‐derived Ea,o and Va,o agree with laboratory results of 275±10 kJ/mol and −6.2±0.6 cm³/mol for Ea,o and Va,o respectively [Shimizu and Kushiro, 1984] measured in experiments at 1673 to 1923 K and 0.5 to 2 GPa. Agreement with the pre‐exponential factor (D*) is poorer, with MD result of ∼10−6.6 for O and laboratory value ∼10−4.7. From ∼15 GPa–25 GPa, Va is ∼0 m³/mol for O, Si, and Al; these species have a positive Va for pressures above 25 GPa (Va,o is ∼ +1 cm³/mol). For pressures ∼15 GPa the majority of the network cations are in 5‐ or 6‐ fold coordination, and more than 20% of the O is in 3‐fold coordination. With increasing pressure, 4‐fold Si and Al decrease monotonically, while 6‐fold Si and Al increase monotonically. Pentahedral Si and Al maximize at nearly the same pressure as O self‐diffusivity.
