Hg-O (Mercury-Oxygen)

The Hg-O system was evaluated by [1999Gum], but no phase diagram was provided. Figure 1 shows the Hg-O phase diagram redrawn from a schematic diagram given in [2004Gum]. HgO exists in several crystalline forms, but the orthorhombic form is the most stable [1999Gum]. Two crystalline forms of HgO2 were quoted in [1999Gum] as stable phases, but they are missing in [2004Gum]. These phases may be metastable because they were reported to be very reactive. In the diagram of [1999Gum], a horizontal line is drawn at 375 C between 0 and 50 at.% O, corresponding to boiling of Hg. This line has been removed in Fig. 1 because, if it exists, it causes immiscibility in the gas phase at high temperatures. Accordingly, Fig. 1 is a phase diagram for condensed phases under pressures. Table 1 shows Hg-O crystal structure data taken from [1999Gum] for phases quoted above.