Bonding and electronic structure of conducting mercury networks: KHgC4n graphite amalgams and Hg3MF6 layers and chains

Abstract

Linear chains, close packed layers, and honeycomb networks of Hg are found in several highly conducting materials. For positively charged Hg systems it is the layers and chains that are calculated to be more stable, whereas for negatively charged ones it is the honeycomb network that is found to be more stable, in agreement with experiments. The electronic structures of these compounds exhibit high densities of state around the Fermi level explaining some of their unusual properties. The small degree of orbital mixing between graphite and the amalgam layer in the graphite compound on the one hand and between Hg and the anions in the linear-chain and layer compounds on the other hand permits a simple interpretation of the results, which is based on a rigid band model. Bonding in the partially negatively charged honeycomb Hg lattice may be approximately described by sp hybridization. The breakup of (Hg/sup 1/2+/) infinity chains into Hg/sub 4//sup 2 +/ ions is derived from a Peierls distortion.