  Icy grains in the interstellar medium and star-formation regions consist of a
variety of materials. Such composite grains interact differently with
cosmic-ray (CR) particles compared to simple single-material grains. We aim to
calculate the spectra of energies and temperatures of mixed-composition grains
undergoing whole-grain heating by CRs. The grains were assumed to consist of a
mixture of carbon and olivine, covered by ices consisting of carbon oxides and
water. The energy and temperature spectra for grains with radii 0.05; 0.1, and
0.2 microns impacted by CRs were calculated for eight values of column density,
relevant to molecular clouds and star-forming cores. The approach takes into
account changes in ice thickness and composition with increasing column
density. These detailed data for CR interaction with interstellar grains are
intended for applications in astrochemical models. The main finding is that the
a more accurate approach on grain heat capacity and other factors prevent a
frequent heating of 0.1 micron or larger icy grains to high temperatures.
