Abundance distribution of ¹⁵O at the beginning (blue) and end (t = 751 s; red) of the simulation in model A. The histograms contain about 24 500 points from a 100 km thick layer, located well above the core-envelope interface (~150 km). The initially narrow and discrete distribution eventually evolves into an inhomogeneous distribution that fits a Gaussian with a dispersion of 25% in the mean value.