Krogmann s salts

For chemists, it is probably not a big surprise that a one-dimensional chain of hydrogen atoms does not exist and that it will immediately decompose into isolated H2 molecules. The Peierls distortion has important consequences for one-dimensional systems, such as polyacetylene with C-C bond-length alterations (instead of equal C-C distances) [74], infinite molecules with platinum-platinum bonding such as Krogmann s salts K2[Pt(CN)4]Xo,3 3H2O with X = Cl or Br [75], or other one-dimensional systems [76], and it also affects three-dimensional systems, in particular elemental structures (see Section 3.4). From a group-theoretical point of view, Peierls distortions are characterized by a loss of translational symmetry in the above example, the nonequidistant chain of H atoms is less symmetrical (in terms of translational symmetry) than the equidistant one. 

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