Calculated chemical abundances of icy species in cold core model. Panel a: abundances, relative to those of the H₂O ice of major icy molecules. The black curve is the average ice thickness $\overline{b}$ on grains, expressed in MLs. Panel b: other selected abundant ice molecules. For convenience, this time $\overline{b}$ was divided by 100. In both panels, solid lines are for Model const with variable E_D, while dotted lines are for Model const_noEd without the variable-E_D approach.