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Zusammenfassung:
Amongst the many rules of thumb that prevail in the search for new
superconductors is a belief that square nets of metal atoms are crucial
to the achievement of high transition temperatures. The recent finding
of superconductivity below 26 K in some intercalated beta-HfNCl phases
suggests that high transition temperatures might be achievable in
compounds with triangular or graphite-like nets as well. Here we present
key features of high level ab initio band structure calculations on the
insulating ZrNCl and HfNCl parent compounds. Electron doping through
intercalation has been modeled within a rigid-band framework. Features
in the energy isosurfaces of the 'doped' compounds are examined for
nesting instabilities of the kind that have been implicated in the
superconducting properties of high-T-c compounds with square nets.
Despite very different electron counts, bonding patterns and atom
topologies, it would seem that certain important aspects of the Fermi
surfaces of the superconducting Zr(Hf)NCl phases are in many respects
very similar to the Fermi surfaces of the cuprate high-T-c
superconductors.
