Crystal Structure of β-Hg

The crystal structure of β-Hg, a pressure induced modification of mercury which is the stable form below 79°K, has been determined. Whereas ordinary (α) mercury crystallizes in a simple rhombohedral lattice, β-Hg is found to be a body-centered tetragonal with a=3.995 A, and b=2.825 A at 77°K. Both phases are superconductors. A brief description of the low temperature x-ray cryostat and camera is given. The relation of α-Hg and β-Hg to Pauling's resonating valence bond theory of metals is discussed.