The Pressure Induced Strain Transition In NiF2
At zero pressure, NiF2 has the well-known rutile (TiO2) structure which belongs to the tetragonal P42/mnm space group, This structure may be viewed as consisting of sheets of linear F-Ni-F molecules oriented along <110> in the sheet at z = 0 and along <110> in the sheet at z = 1/2. Compounds with this rutile structure have received considerable attention as candidates for pressure-induced phase transitions resulting from a softening of the acoustic mode corresponding to the effective elastic consant 1/2(C11 - C12) [1–3]. However, before the present structural measurements on NiF2, the second-order strain transition in TeO2, which has a slightly distorted rutile structure, was the only such transition where the relevant structural parameters, elastic constants, and acoustic phonon modes had been studied in detail at high pressure and compared with Landau’s theory [4–8].
KeywordsUnit Cell Volume Atomic Position Rutile Structure Thermal Displacement Anisotropic Thermal Parameter
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