TY - JOUR
T1 - High-pressure crystal structure of kosmochlor, NaCrSi2O6, and systematics of anisotropric compression in pyroxenes
AU - Origlieri, Marcus J.
AU - Downs, Robert T
AU - Thompson, Richard M.
AU - Pommier, Carolyn J.S.
AU - Denton, M. Bonner
AU - Harlow, George E.
PY - 2003/7
Y1 - 2003/7
N2 - The crystal structure of synthetic kosmochlor, NaCrSi2O6, was studied using single crystal X-ray diffraction at high pressure. A four-pin diamond anvil cell, with 4:1 methanol:ethanol pressure medium, was used to achieve pressures to 9.28 GPa. Unit-cell data were collected at 20 pressures, and intensity data were collected at 13 of these pressures. Fitting the P-V data to a third-order Birch-Murnaghan equation yields Vo = 418.84(3) Å3, Kc = 134(1) GPa 1, and K1o = 2.0(3). Anisotropic compression was observed with unit strain axial ratios of 1:1.82:2.08. The CrO6 octahedron has a bulk modulus Ko = 90(16) GPa1, while the SiO4 tetrahedron has Ko = 313(55) GPa 1, both with K1o= 4. An o-type rotation of the O3-O3-03 linkage was observed with pressure, with <03-03-03 decreasing from 172.8(2)° to 166.1(7)°. Compression in kosmochlor is related to the stacking directions of distorted cubic closest packed O atom monolayers. Unit strain ellipsoids for diopside. hedenbergite, spodumene (C2/c and P21/c), LiScSi2O6 (C2/c and P2l/c), clinoenstatite, orthoenstatite. and anisotropy of olivine and pyroxene.
AB - The crystal structure of synthetic kosmochlor, NaCrSi2O6, was studied using single crystal X-ray diffraction at high pressure. A four-pin diamond anvil cell, with 4:1 methanol:ethanol pressure medium, was used to achieve pressures to 9.28 GPa. Unit-cell data were collected at 20 pressures, and intensity data were collected at 13 of these pressures. Fitting the P-V data to a third-order Birch-Murnaghan equation yields Vo = 418.84(3) Å3, Kc = 134(1) GPa 1, and K1o = 2.0(3). Anisotropic compression was observed with unit strain axial ratios of 1:1.82:2.08. The CrO6 octahedron has a bulk modulus Ko = 90(16) GPa1, while the SiO4 tetrahedron has Ko = 313(55) GPa 1, both with K1o= 4. An o-type rotation of the O3-O3-03 linkage was observed with pressure, with <03-03-03 decreasing from 172.8(2)° to 166.1(7)°. Compression in kosmochlor is related to the stacking directions of distorted cubic closest packed O atom monolayers. Unit strain ellipsoids for diopside. hedenbergite, spodumene (C2/c and P21/c), LiScSi2O6 (C2/c and P2l/c), clinoenstatite, orthoenstatite. and anisotropy of olivine and pyroxene.
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U2 - 10.2138/am-2003-0711
DO - 10.2138/am-2003-0711
M3 - Article
AN - SCOPUS:0038235674
SN - 0003-004X
VL - 88
SP - 1025
EP - 1032
JO - American Mineralogist
JF - American Mineralogist
IS - 7
ER -