Hydrogen bond effects on compressional behavior of isotypic minerals: high-pressure polymorphism of cristobalite-like Be(OH)2

Hannah Shelton, Madison C. Barkley, Robert T Downs, Ronald Miletich, Przemyslaw Dera

Research output: Contribution to journalArticle

Abstract

Three isotypic crystals, SiO2 (α-cristobalite), ε-Zn(OH)2 (wülfingite), and Be(OH)2 (β-behoite), with topologically identical frameworks of corner-connected tetrahedra, undergo displacive compression-driven phase transitions at similar pressures (1.5–2.0 GPa), but each transition is characterized by a different mechanism resulting in different structural modifications. In this study, we report the crystal structure of the high-pressure γ-phase of beryllium hydroxide and compare it with the high-pressure structures of the other two minerals. In Be(OH)2, the transition from the ambient β-behoite phase with the orthorhombic space group P212121 and ambient unit cell parameters a = 4.5403(4) Å, b = 4.6253(5) Å, c = 7.0599(7) Å, to the high-pressure orthorhombic γ-polymorph with space group Fdd2 and unit cell parameters (at 5.3(1) GPa) a = 5.738(2) Å, b = 6.260(3) Å, c = 7.200(4) Å takes place between 1.7 and 3.6 GPa. This transition is essentially second order, is accompanied by a negligible volume discontinuity, and exhibits both displacive and reversible character. The mechanism of the phase transition results in a change to the hydrogen bond connectivities and rotation of the BeO4 tetrahedra.

Original languageEnglish (US)
Pages (from-to)571-586
Number of pages16
JournalPhysics and Chemistry of Minerals
Volume43
Issue number8
DOIs
StatePublished - Sep 1 2016

Keywords

  • Behoite
  • Beryllium hydroxide
  • Cristobalite
  • High pressure
  • Hydrogen bonding
  • Phase transitions
  • SiO

ASJC Scopus subject areas

  • Materials Science(all)
  • Geochemistry and Petrology

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