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Polymorphism of NaHg: The First Experimental Observation of a Reversible, Temperature Driven B2 (CsCl) - B32 (NaTl) Phase Transition

Matthiasand Rochnia ; Anorganische Chemie II, Fb8, Universitat-GH Siegen, D-57068 Siegen
Hans-Jörg Deiseroth ; Anorganische Chemie II, Fb8, Universitat-GH Siegen, D-57068 Siegen

Puni tekst: engleski pdf 17.221 Kb

str. 701-708

preuzimanja: 149



Based on combined X-ray analyses and thermal investigations, the intermetallic compound NaHg is shown to exist in three different modifications (a-, (1- and y-NaHg). The already known low temperature modification a-NaHg is an orthorhombically distorted variant of the CsCl (B2) structure. At 165 °C, a-NaHg transforms in a reconstructive first order transition of (1-NaHg, a slightly rhombo- hedrally distorted variant of the NaTl (B32) type (a = 5.071(8), c = 12.668(31) A, space group R3m). In a subsequent displacive first order transition at 176 °C, y-NaHg, crystallizing in the undistorted cubic NaTl (B32) type (a = 7.253, Å, space group: Fd3m), is formed. To our knowledge, this is the first observation of a temperature driven B2/B32 phase transition.

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