Seismic properties of a selected set of models. Top left panel: échelle diagram for the best model A7, optimized on the basis of the individual frequencies and including – or not – the correction for surface effects. Star symbols represent the observed frequencies, while black squares, blue circles, and red diamonds denote the model frequencies for angular degrees ℓ = 0,1, and 2. In grey, we indicate the corresponding data before correction for surface effects. Top right panel: comparison of observed large frequency separations for case A7 (corrected frequencies). The symbols are the same as in the top right figure. Bottom left panel: comparison of the observed frequency separation ratios rr_{01 / 10}(n) for a selected set of models, including the best model A7 (continuous blue line). Results for models A7-YM-244 (pentagons) and A7-YM335 (diamonds) illustrate the effect of the Y₀-M degeneracy. Results for model K6 (continuous red line) show the effect of including convective penetration below the convective envelope, while results for model I7 (dashed orange line) show the effect of a moderate overshooting of the convective core. Bottom right panel: same as in the bottom left figure, but for the r₀₂(n) frequency separation ratios.