High-pressure raman investigation of mutual solubility and compound formation in (formula presented) and (formula presented)

Abstract

In this study, the mixed solid phases of the molecular systems (Formula presented) and (Formula presented) have been investigated up to 13 GPa using Raman spectroscopy and so-called (Formula presented) and (Formula presented) scans. Both systems show a rich variety of solid phases. In (Formula presented) a van der Waals compound has been found. The solubility of (Formula presented) in solid Xe is about 7.5 mol %, while the solubility of the larger Xe atoms into the β and δ phases of (Formula presented) is higher. In (Formula presented) two van der Waals compounds have been detected. The Raman spectrum of one of these compounds is very similar to that of (Formula presented) (Formula presented) does not dissolve into solid Ne, while Ne does dissolve into the β and δ phases of (Formula presented) even though the atomic diameter of Ne is considerably smaller than the molecular one of (Formula presented) Analogous to (Formula presented) the Ne and Xe atoms are mainly located at the a sites in the (Formula presented) phase. For (Formula presented) in contrast to (Formula presented) the (Formula presented)-(Formula presented) transition shifts to higher pressure. The (Formula presented)-(Formula presented) transition is not shifted for (Formula presented) 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, α, is only a very rough indication for the phase behavior of mixed molecular systems at high pressure. © 1999 The American Physical Society.