Calculated and reference opacities of astrophysical dust, plotted as a function of the wavelength. Dotted lines labeled with OH94 refer to bare grains as well as to grains with icy mantles by Ossenkopf & Henning (1994). Opacities for grains with pure CO and CO₂ icy mantles, computed for optical constants of the present work, are depicted by the solid and dashed lines, respectively. The label “V” denotes the volume ratio of the icy mantles to the refractory material, indicating bare grains (V = 0, black) and grains with thick mantles (V = 4.5, red).