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Title: Petalite under pressure: Elastic behavior and phase stability

The lithium aluminosilicate mineral petalite (LiAlSi 4O 10) has been studied using high-pressure single-crystal X-ray diffraction (HP-XRD) up to 5 GPa. Petalite undergoes two pressure-induced first-order phase transitions, never reported in the literature, at ca. 1.5 and 2.5 GPa. The first of these transforms the low-pressure α-phase of petalite (P2/c) to an intermediate β-phase that then fully converts to the high-pressure β-phase at ca. 2.5 GPa. The α→β transition is isomorphic and is associated with a commensurate modulation that triples the unit cell volume. Analysis of the HP-XRD data show that although the fundamental features of the petalite structure are retained through this transition, there are subtle alterations in the internal structure of the silicate double-layers in the β-phase relative to the α-phase. Measurement of the unit cell parameters of petalite as a function of pressure, and fitting of the data with 3rd order Birch-Murnaghan equations of state, has provided revised elastic constants for petalite. The bulk moduli of the α and β-phases are 49(1) and 35(3) GPa, respectively. These values indicate that the compressibility of the- phase of petalite lies between the alkali feldpsars and alkali feldspathoids, whereas the β-phase has a compressibility more comparable with layered silicates. Structuremore » analysis has shown that the compression of the -phase is facilitated by the rigid body movement of the Si 2O 7 units from which the silicate double-layers are constructed.« less
 [1] ;  [1] ;  [2] ;  [1] ;  [3]
  1. Virginia Polytechnic Inst. and State Univ. (Virginia Tech), Blacksburg, VA (United States). Dept. of Geosciences
  2. irginia Polytechnic Inst. and State Univ. (Virginia Tech), Blacksburg, VA (United States). Dept. of Chemistry
  3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Quantum Condensed Matter Division
Publication Date:
Grant/Contract Number:
AC05-00OR22725; EAR-1118691; CHE-0131128
Accepted Manuscript
Journal Name:
American Mineralogist
Additional Journal Information:
Journal Volume: 100; Journal Issue: 4; Journal ID: ISSN 0003-004X
Mineralogical Society of America
Research Org:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
36 MATERIALS SCIENCE; phase transition; high pressure; equation of state; petalite; single-crystal x-ray diffraction
OSTI Identifier: