Effects of opacity values derived for grains under DHS approach by assuming NK1 and NK2 values. Panel a shows the synthetic protostellar spectrum with H₂O ice and silicate absorption bands calculated from opacity models based on NK1 (black) and NK2 (red) refractive index values. The black and red and dashed lines over the 3 µm feature are the continuum. The blue box around 13 µm highlights the absence of the H₂O libration band in the spectrum derived from NK2 values. Panel b displays the same as panel a but for porous ice. Panels c and d present the H₂O ice column density derived from the optical depth spectrum using compact and porous ices, respectively. Finally, panels e and f compare the ice column densities from both cases (grey: NK1; red: NK2).