  We use computer simulations to investigate the effect of salt on homogeneous
ice nucleation. The melting point of the employed solution model was obtained
both by direct coexistence simulations and by thermodynamic integration from
previous calculations of the water chemical potential.
  Using a Seeding approach, in which we simulate ice seeds embedded in a
supercooled aqueous solution, we compute the nucleation rate as a function of
temperature for a 1.85 NaCl mole per water kilogram solution at 1 bar. To
improve the accuracy and reliability of our calculations we combine Seeding
with the direct computation of the ice-solution interfacial free energy at
coexistence using the Mold Integration method. We compare the results with
previous simulation work on pure water to understand the effect caused by the
solute. The model captures the experimental trend that the nucleation rate at a
given supercooling decreases when adding salt. Despite the fact that the
thermodynamic driving force for ice nucleation is higher for salty water for a
given supercooling, the nucleation rate slows down with salt due to a
significant increase of the ice-fluid interfacial free energy. The salty water
model predicts an ice nucleation rate that is in good agreement with
experimental measurements, bringing confidence in the predictive ability of the
model.
