Pressure dependence of transport and optical properties of Ag2HgI4

Electrical conductivity—differential thermal analysis measurements on some MnHgI4 complexes

The thermal decomposition of some tetraiodomercurates

High temperature reflectance spectroscopy: application to thermochromic compounds☆

Raman spectra and phonon pressure dependencies are reported for the spinel-related iodides A2HgI4, (A = Ag, Cu, Tl and 1/2Pb) at high pressures in a diamond anvil cell. In each case the upper pressure limit of observation was set by changes in band gap which caused darkening and photodecomposition. New phase transitions were found for Cu2HgI4 (8 and 25 kbar), Tl2HgI4 (11.5 kbar) and PbHgI4 (7 and 14 kbar). Transitions in Ag2HgI4 were located at 3.3, 5.9 and 8.1 kbar, confirming and extending earlier evidence. The β-Ag2HgI4 to phase II transition at 3.3 kbar appears to be second-order in type. Using Landau's theory, Ag2HgI4 II was shown to adopt space group C. Similarly, at the I/II transition in Cu2HgI4, the new phase (II) can have either D or C symmetry.

J. B. Maginnis

Papers

Heat-Sensitive Color Changes in Some Inorganic Chemicals