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The Use of Quartz as an Internal Pressure Standard in High‐Pressure Crystallography
Author(s) -
Angel R. J.,
Allan D. R.,
Miletich R.,
Finger L. W.
Publication year - 1997
Publication title -
journal of applied crystallography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.429
H-Index - 162
ISSN - 1600-5767
DOI - 10.1107/s0021889897000861
Subject(s) - quartz , equation of state , diamond anvil cell , diffraction , fluorite , volume (thermodynamics) , analytical chemistry (journal) , single crystal , crystallography , chemistry , pressure measurement , x ray crystallography , powder diffraction , crystal (programming language) , materials science , thermodynamics , optics , metallurgy , physics , programming language , chromatography , computer science
The unit‐cell parameters of quartz, SiO 2 , have been determined by single‐crystal diffraction at 22 pressures to a maximum pressure of 8.9 GPa (at room temperature) with an average precision of 1 part in 9000. Pressure was determined by the measurement of the unit‐cell volume of CaF 2 fluorite included in the diamond‐anvil pressure cell. The variation of quartz unit‐cell parameters with pressure is described by: a −4.91300 (11) = −0.0468 (2) P + 0.00256 (7) P 2 − 0.000094 (6) P 3 , c − 5.40482 (17) = − 0.03851 (2) P + 0.00305 (7) P 2 − 0.000121 (6) P 3 , where P is in GPa and the cell parameters are in ångstroms. The volume–pressure data of quartz are described by a Birch–Murnaghan third‐order equation of state with parameters V 0 = 112.981 (2) å 3 , K T0 = 37.12 (9) GPa and K ′ = 5.99 (4). Refinement of K ′′ in a fourth‐order equation of state yielded a value not significantly different from the value implied by the third‐order equation. The use of oriented quartz single crystals is proposed as an improved internal pressure standard for high‐pressure single‐crystal diffraction experiments in diamond‐anvil cells. A measurement precision of 1 part in 10 000 in the volume of quartz leads to a precision in pressure measurement of 0.009 GPa at 9 GPa.