The resistivity of mixed valence compound Cs2Au2Cl6 at high pressure and low temperatures

Crystal Structure of Mixed-Valence Gold Compound, Cs2AuIAuIIICl6 up to 18GPa.

“…From these viewpoints, the relationship between the physical properties and the crystal structure of the perovoskite-type halides, Cs2AuIAuIIIX6 (X=Cl, Br, I) ( Fig. 1), which are well known as three-dimensional halogenbridged mixed-valence gold compounds, have been systematically investigated [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. Its structure consists of a threedimensional metal-halogen framework formed by elongated octahedra with AuIII and compressed octahedra with AuI sharing their coners.…”

Mixed valence model for superconductivity

“…The electron count corresponds to exactly one hole per site. CsAuX 3 or Cs 2 AuX 4 are semiconductors (at low pressure) with large activation energy [30,31]. The conductivity is increased by several orders of magnitude at high pressures of a few GPa [30][31][32][33], but superconductivity has not been reported.…”

“…CsAuX 3 or Cs 2 AuX 4 are semiconductors (at low pressure) with large activation energy [30,31]. The conductivity is increased by several orders of magnitude at high pressures of a few GPa [30][31][32][33], but superconductivity has not been reported. High pressure leads to decreased activation barrier (see below) and at the same time to an insulator to metal transition, of obvious relevance also to superconductivity [3,16].…”

“…High pressure leads to decreased activation barrier (see below) and at the same time to an insulator to metal transition, of obvious relevance also to superconductivity [3,16]. Well's salt, CsAuCl 3 , is probably the first and best-known example of disproportionation in gold compounds [29][30][31][32][33]. At normal pressure the distances of the xy-plane are 0.4 smaller in Au(III)-Cl than corresponding distances for Au(I)-Cl.…”

Mixed Valency Chemistry: A Survey of 10 Years Progress

“…3. No information has been published about the structures of WRS crystals at high pressure, but it is worth pointing out that in another halide-bridged mixed valency chain compound Cs,[AuCl,]-[AuCl,] (Well's Salt) there is definite evidence for a shift in the Au(1)-CI and Au(II1)-CI bond lengths with pressure (Day, Vettier and Parisot, 1978), so that at 60 kbar they become equal (Denner, Schulz and d'Amour, 1978) and the substance is then a metal (Keller, Fenner and Holzapfel, 1974).…”