Hydrogen bond effects on compressional behavior of isotypic minerals: high-pressure polymorphism of cristobalite-like Be(OH)2
- Univ. of Hawaii, Honolulu, HI (United States)
- Univ. of Arizona, Tucson, AZ (United States); Arizona Historical Society, Phoenix, AZ (United States)
- Arizona Historical Society, Phoenix, AZ (United States)
- Univ. Wien (Austria)
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 drivenphase 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.
- Research Organization:
- Carnegie Inst. of Science, Argonne, IL (United States)
- Sponsoring Organization:
- USDOE National Nuclear Security Administration (NNSA)
- Grant/Contract Number:
- NA0002006
- OSTI ID:
- 1338333
- Journal Information:
- Physics and Chemistry of Minerals, Vol. 43, Issue 8; ISSN 0342-1791
- Publisher:
- SpringerCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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