Molar ratio C:O in ices (left scale) and its deviation relative to the solar abundance (right scale), for one particular simulation (Σ₀ = 95.844 g cm^-2, a_core = 46, γ = 0.9), as a function of the distance to the star, and for non-irradiated (black lines) and irradiated (grey lines) models, including chemical variation (CO:CO₂ molar ratio), and with (dashed lines) and without (solid lines) clathrates.