Does metallic ammonium exist?

  title={Does metallic ammonium exist?},
  author={David J. Stevenson},
THE ammonium ion NH4+ behaves in many ways like an alkali metal ion. This led Ramsey1 to propose that monovalent ammonium metal (NH4+ ions immersed in an almost uniform, degenerate sea of electrons) is stable at pressures much lower than typical insulator–metal transition pressures2 of megabars ∼1011 Pa (105 Pa = 1 bar). Subsequently, it was estimated3 that the transition from a mixture of NH3 and H2 molecules to metallic ammonium, occurs at a pressure of less than 2.5×1010 Pa. If this estimate… 

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