Metals and superconductors: molecular analogs of atomic hydrogen.

One for the half: recent work on atomic hydrogen and neutral radical heterocyclic molecules has moved the field of spin S=1/2 solids closer to the realization of synthetic intrinsic metals and superconductors. High-pressure experiments on hydrogen and chalcogenide-nitrogen molecules show evidence of metallic character. The molecular radicals exhibit a positive temperature coefficient of resistance under pressure-the classic signature of a metal.