In this study, the mixed solid phases of the molecular systems Xe-N2 and Ne-N2 have been investigated up to 13 GPa using Raman spectroscopy and so-called v-T and p-T scans. Both systems show a rich variety of solid phases. In Xe-N2 a van der Waals compound has been found. The solubility of N2 in solid Xe is about 7.5 mol %, while the solubility of the larger Xe atoms into the ß and d phases of N2 is higher. In Ne-N2 two van der Waals compounds have been detected. The Raman spectrum of one of these compounds is very similar to that of He(N2)11. N2 does not dissolve into solid Ne, while Ne does dissolve into the ß and d phases of N2, even though the atomic diameter of Ne is considerably smaller than the molecular one of N2. Analogous to Ar-N2, the Ne and Xe atoms are mainly located at the a sites in the d* phase. For Ne-N2, in contrast to Xe-N2, the ß*-d* transition shifts to higher pressure. The e*-d* transition is not shifted for Ne-N2. The results have been compared with computer simulations and analytical theories for hard-sphere systems. It is shown that the ratio of the diameters of the molecules, a, is only a very rough indication for the phase behavior of mixed molecular systems at high pressure. ©1999 The American Physical Society.