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We have investigated the high-pressure behavior of PbCrO. In particular, we have probed the existence of structural transitions under high pressure (at 4.5 GPa) by single-crystal X-ray diffraction and density functional theory calculations. The structural sequence of PbCrO is different than previously determined. Specifically, we have established that PbCrO, under pressure, displays a monoclinic-tetragonal phase transition, with no intermediate phases between the low-pressure monoclinic monazite structure (space group P2/ n) and the high-pressure tetragonal structure. The crystal structure of the high-pressure polymorph is, for the first time, undoubtedly determined to a tetragonal scheelite-type structure (space group I4/ a) with unit-cell parameters a = 5.1102(3) Å and c = 12.213(3) Å. These findings have been used for a reinterpretation of previously published Raman and optical-absorption results. Information of calculated infrared-active phonons will be also provided. In addition, the pressure dependence of the unit-cell parameters, atomic positions, bond distances, and polyhedral coordination are discussed. The softest and stiffest direction of compression for monazite-type PbCrO are also reported. Finally, the theoretical pressure dependence of infrared-active modes is given, for the first time, for both polymorphs.
This article was published in the following journal.
Name: Inorganic chemistry
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The scattering of x-rays by matter, especially crystals, with accompanying variation in intensity due to interference effects. Analysis of the crystal structure of materials is performed by passing x-rays through them and registering the diffraction image of the rays (CRYSTALLOGRAPHY, X-RAY). (From McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)
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