Hydrostatic compression and crystal structure of pyrope to 33 GPa

In situ analysis of garnet inclusion in diamond using single-crystal X-ray diffraction and X-ray micro-tomography

“…Interpolation of Zhang's et al (1998) data for pure pyrope to 1 GPa shows that the oxygen atomic coordinates x and z remain virtually unchanged, whereas the y coordinate increases by only 0.0006, i.e., well below uncertainties of measurements based on X-ray diffraction. This value should approximately correspond to the predicted change for a pressure variation from 1 GPa to room conditions.…”

“…Such low internal pressures would have very little effect on the structural parameters (atomic coordinates and unit-cell edge) of the rigid crystal structure of garnet (cf. Zhang et al, 1998) and therefore on their estimated chemical compositions.…”

Properties of Complex Inorganic Solids

“…We used only the data for pressures below 30 GPa in order to use a procedure which is similar to that used in the data analysis of the experimental studies (Hazen and Finger 1989;Leger et cd. 1990;Olijnyk et al 1991;Lager and Von Dreele 1996;Zhang et al 1998;Conrad et al 1999).…”

“…The unit cell of an anhydrous garnet contains 160 atoms which makes quantum mechanical studies of these systems extremely demanding. However, experimental data on highpressure behaviour of rock-forming garnets are extremely scarce (Hazen and Finger 1989;Leger et al 1990;Olijnyk et al 1991;Lager and Von Dreele 1996;Zhang et al 1998;Conrad et al 1999) and often inaccurate as will be discussed below. First principles modelling offers therefore the best chance of predicting the behaviour of garnets under the extreme conditions found in the crust and upper mantle, thereby allowing a deeper understanding of the response of the garnet structure to increasing pressure.…”

Influence of Chemical Composition and Water on the Bulk Modulus of Pyrope

“…Equations of state of the end members, pyrope and almandine (Fe 3 Al 2 (SiO 4 ) 3 ), have been also studied (O'Neill, Bass, Y. Wang et al, 1998;Zhang, Ahsbahs, & Kutoglu, 1998;Zhang, Ahsbahs, Kutoglu, & Geiger, 1999). Compositional effect on bulk moduli of natural garnet in grossularalmandine-pyrope system have been examined (Jiang, Speziale, & Duffy, 2004;O'Neill, Bass, Smyth, & Vaughan, 1989).…”