TY - JOUR
T1 - High-pressure X-ray study of LiCrSi2O6 clinopyroxene and the general compressibility trends of Li-clinopyroxenes.
AU - Periotto, Benedetta
AU - Angel, Ross J.
AU - Nestola, Fabrizio
AU - Balic Zunic, Tonci
AU - Fontana, Cinzia
AU - Pasqual, Daria
AU - Alvaro, Matteo
AU - Redhammer, Günther J.
PY - 2013/5
Y1 - 2013/5
N2 - High-pressure single-crystal X-ray diffraction measurements of synthetic LiCrSi2O6 clinopyroxene (with space group P21/c) were performed in a diamond-anvil cell up to 7.970 GPa. No phase transition has been observed within the pressure range investigated, but the elastic behavior at lower pressures (up to ~2.5 GPa) is affected by an anomalous softening due to the proximity of the phase transition to the HT-C2/c phase at 330 K and at ambient pressure. A third-order Birch-Murnaghan equation of state fitted to the compression data above 2.5 GPa yields a bulk modulus KT0 = 93(2) GPa and its first derivative K′ = 8.8(6). The structural data measured up to 7. 970 GPa confirm that the space group P21/c is maintained throughout the whole pressure range investigated. The atomic parameters, obtained from the integrated diffraction intensities, suggest that the Li coordination polyhedron changes its coordination number from 5 to 6 at 6-7 GPa by means of the approach of the bridging O atom, related to the increased kinking of the B tetrahedral chain. Furthermore, at higher pressures, the structural evolution of LiCrSi2O6 provides evidence in the variation of kinking angles and bond lengths of a potential phase transition above 8 GPa to the HP-C2/c space group. A comparison of the Li-clinopyroxenes (M1 = Cr, Al, Sc, Ga, Mg + Fe) previously investigated and our sample shows that their elastic behavior and structural mechanisms of compression are analogous.
AB - High-pressure single-crystal X-ray diffraction measurements of synthetic LiCrSi2O6 clinopyroxene (with space group P21/c) were performed in a diamond-anvil cell up to 7.970 GPa. No phase transition has been observed within the pressure range investigated, but the elastic behavior at lower pressures (up to ~2.5 GPa) is affected by an anomalous softening due to the proximity of the phase transition to the HT-C2/c phase at 330 K and at ambient pressure. A third-order Birch-Murnaghan equation of state fitted to the compression data above 2.5 GPa yields a bulk modulus KT0 = 93(2) GPa and its first derivative K′ = 8.8(6). The structural data measured up to 7. 970 GPa confirm that the space group P21/c is maintained throughout the whole pressure range investigated. The atomic parameters, obtained from the integrated diffraction intensities, suggest that the Li coordination polyhedron changes its coordination number from 5 to 6 at 6-7 GPa by means of the approach of the bridging O atom, related to the increased kinking of the B tetrahedral chain. Furthermore, at higher pressures, the structural evolution of LiCrSi2O6 provides evidence in the variation of kinking angles and bond lengths of a potential phase transition above 8 GPa to the HP-C2/c space group. A comparison of the Li-clinopyroxenes (M1 = Cr, Al, Sc, Ga, Mg + Fe) previously investigated and our sample shows that their elastic behavior and structural mechanisms of compression are analogous.
U2 - 10.1007/s00269-013-0569-5
DO - 10.1007/s00269-013-0569-5
M3 - Journal article
SN - 0342-1791
VL - 40
SP - 387
EP - 399
JO - Physics and Chemistry of Minerals
JF - Physics and Chemistry of Minerals
IS - 5
ER -