Pressure-induced disordering of sodium potassium sulfates and chromates

Frederick E. Bernardin, William S. Hammack

Research output: Contribution to journalArticlepeer-review


Raman scattering and energy-dispersive x-ray diffraction in a diamond-anvil cell were used to study the salts (Formula presented), (Formula presented)Na((Formula presented)(Formula presented), (Formula presented), and (Formula presented)Na((Formula presented)(Formula presented) to pressures of 22.5 GPa. These measurements reveal that the (Formula presented) and (Formula presented) tetrahedra in the monopotassium salts become disordered, while those in the tripotassium salts stay ordered. This disordering occurs without a significant change in the structural arrangement of the cations. We suggest that the disordering results from an impeded ferroelastic phase transition, which causes the zone boundaries, and therefore the (Formula presented) and (Formula presented) tetrahedra, to be distorted. The four salts are related to one of two structures: The tripotassium salts are isostructural, the monopotassium salts are closely related. The two structures differ by one symmetry element, which leaves the neighboring tetrahedra inequivalent. It is this difference that causes only one of the structures to form distorted zone boundaries.

Original languageEnglish (US)
Pages (from-to)7026-7033
Number of pages8
JournalPhysical Review B - Condensed Matter and Materials Physics
Issue number10
StatePublished - 1996
Externally publishedYes

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics


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