The high-pressure crystal chemistry of low albite and the origin of the pressure dependency of Al-Si ordering

R. T. Downs, R. M. Hazen, L. W. Finger

Research output: Contribution to journalArticle

65 Scopus citations

Abstract

Structural and volume compressibility data for low albite were obtained by single-crystal X-ray diffraction methods at pressures up to ~4 GPa. The bulk modulus was determined to be 54(1) GPa, with a pressure derivative of 6(1). Intensity data were collected, and structures were refined at 0.00, 0.44, 1.22, 2.68, and 3.78 GPa. With increasing pressure, (1) the volumes of the TO4 tetrahedra do not vary, (2) the volume of the NaO7 polyhedron varies linearly with the volume of the unit cell and (3) Si-O-Si angles increase or remain constant, but only Al-O-Si angles decrease, which is consistent with the smaller force constant of the Al-O-Si vs. Si-O-Si angle. It is concluded that compression is accomplished through the bending of Al-O-Si angles, which squeezes together the chains of four-membered rings that run parallel to [001] and that are separated by zigzag channels containing Na atoms. -from Authors

Original languageEnglish (US)
Pages (from-to)1042-1052
Number of pages11
JournalAmerican Mineralogist
Volume79
Issue number11-12
StatePublished - Jan 1 1994
Externally publishedYes

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology

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